Information storage medium and information recording/playback system

ABSTRACT

There are provided an information storage medium capable of real-time recording/playback of digital moving picture information, and a digital information recording/playback system using this medium. In a medium that records/plays back data including video data and control information, the control information (DA 21  in FIG.  4;  RTR_VMG in FIG.  30 ) includes information (VOBU entry in FIG.  31 ) for accessing a specific portion (VOBU) of the video data.

CROSS-REFERENCE TO RELATED APPLICATIONS

This divisional application claims the benefit of priority under 35U.S.C. §120 to U.S. application Ser. No. 12/622,116 filed on Nov. 19,2009, which is a divisional of application Ser. No. 11/501,892 (now U.S.Pat. No. 7,636,513), filed on Aug. 10, 2006, which is a divisional ofU.S. application Ser. No. 10/801,701 (now U.S. Pat. No. 7,200,326),filed on Mar. 17, 2004, which is a divisional of U.S. application Ser.No. 10/669,525 (now U.S. Pat. No. 7,536,081), filed on Sep. 25, 2003,which is a divisional of U.S. application Ser. No. 09/939,582 (now U.S.Pat. No. 6,654,543), filed on Aug. 28, 2001, which is a divisional ofU.S. application Ser. No. 09/643,985 (now U.S. Pat. No. 6,549,721),filed on Aug. 23, 2000, the contents of each of which are incorporatedherein by reference. U.S. application Ser. No. 09/643,985 is acontinuation of Application No. PCT/JP99/00795 (not published inEnglish), filed on Feb. 23, 1999. This application is based upon andclaims the benefit of priority from the prior Japanese PatentApplications No. 10-040876, filed Feb. 23, 1998; No. 10-040877, filedFeb. 23, 1998; and No. 10-040879, filed Feb. 23, 1998, the entirecontents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

The present invention relates to an information storage mediumrepresented by a large-capacity optical disc and a digital informationrecording/playback system using the medium.

In particular, the present invention relates to a DVD (digital versatiledisc) recording/playback system that considers real-time recording of amoving picture.

The present invention also relates to a recording/playback system whichcan guarantee continuous playback (or continuous recording) uponcontinuously playing back (or continuously recording) information usingplayback devices (disc drives) having various access performances.

Furthermore, the present invention relates to a recording/playbacksystem which can prevent any playback timing errors of video informationand audio information recorded on the medium.

DESCRIPTION OF PRIOR ART

In recent years, systems for playing back the contents of optical discsthat have recorded video (moving picture) data, audio data, and the likehave been developed, and have prevailed for the purpose of playing backmovie software, karaoke, and so on like LDs (laser discs), video CDs(video compact discs), and the like.

Among such systems, a DVD (Digital Versatile Disc) standard that usesMPEG2 (Moving Picture Experts Group) international standard, and adoptsan audio compression scheme such as AC-3 (digital audio compression) orthe like has been proposed. The DVD standard includes read-only DVDvideo (or DVD-ROM), write-once DVD-R, and erasable/rewritable DVD-RW (orDVD-RAM).

The DVD video (DVD-ROM) standard supports MPEG2 as a movie compressionscheme, and AC3 audio and MPEG audio in addition to linear PCM as anaudio recording scheme, in accordance with MPEG2 system layer.Furthermore, this DVD video standard is configured by appendingsub-picture data for superimposed dialogs obtained byrunlength-compressing bitmap data, and control data (navigation data)for playback control such as fastforwarding, rewinding, data search, andthe like.

Also, this standard supports ISO9660 and UDF Bridge format to allow acomputer to read data. Hence, a personal computer environment can handlevideo information of DVD video.

Problem

However, a personal computer system and DVD recording/playback systemuse different appropriate information processing methods, and it isdifficult for the personal computer to record/play back movieinformation for a long period of time continuously (without beinginterrupted).

More specifically, in the personal computer environment, when file datais to be changed, a process for re-recording the entire changed filedata on a free area of an information storage medium (HDD or the like)is done. At this time, the re-recording position on the informationstorage medium is determined irrespective of the file data recordingposition before change. The file data recording position before changeis released as a small free area after the change. If such change offile data is frequently repeated, small free areas are scattered in avermicular pattern at physically separated positions on the medium. As aresult, upon recording new file data, that data is recorded on aplurality of vermiculated free areas while being fragmented. This stateis called fragmentation.

In the information process of the personal computer, information (filedata) used is readily scattered (fragmented) on the disc. Even when afile to be read out has been fragmented, required information can readout from a disc by sequentially playing back such fragments recordedrandomly. This fragmentation slightly prolongs the required read-outtime of a file, but the user does not feel disrupted if a high-speed HDDis used.

However, when recorded information (MPEG-compressed moving picture data)has been fragmented in a DVD recording/playback system, if suchfragments recorded randomly are to be played back in turn, movingpicture playback may often be interrupted. Especially, since an opticaldisc drive requires a longer seek time of an optical head than ahigh-speed disc drive such as an HDD or the like, the playback video isreadily interrupted during seeking fragmented information in the DVDrecording/playback system that records/plays back an MPEG moving picturevideo on/from an optical disc (DVD-RAM disc or the like), resulting inpoor practicality of the current system.

When both personal computer data and DVD moving picture data arerecorded, fragmentation is more likely to occur. Therefore, the DVDrecording/playback system that includes the personal computerenvironment has no feasibility unless a very high-speed optical discdrive is developed, and a large-size buffer can be mounted at practicalcost.

On the medium that records video information (cells), upon repeatingediting and partial deletion of recorded information, individual piecesof video information lie scattered or straggle on the medium. When suchscattered or straggling video information group is to be continuouslyplayed back according to a specific order, frequent accesses arerequired. During these accesses, since a recorded information group (aseries of cells) cannot be played back from the medium, playback isinterrupted.

That is, when a specific playback device (disc drive) plays back ascattered or straggling video information group while making frequentaccesses, if the access frequency has exceeded a specific number oftimes, it becomes impossible (for that drive) to continuously outputrecorded information, thus disturbing seamless playback (without anyinterrupt).

Furthermore, the frequency shift of the reference clocks of a normaldigital audio recorder is approximately 0.1%. When sound sourceinformation digitally recorded by a digital video tape (DAT) recorder isoverdubbed on video information already recorded on a DVD-RAM disc bydigital copy, the reference clocks between the video information andaudio information may have an error of around 0.1%. Such reference clockerror becomes so large that it cannot be ignored upon repeating thedigital copy (or nonlinear edit using a personal computer or the like),and appears as interrupted playback tones or a phase shift betweenplayback channels.

In some cases, audio information corresponding to a specific video packis stored in an audio pack at a location largely separated from thatvideo pack. When a specific cell is re-recorded at another location onan information storage medium, synchronization between video and audiopacks fails if packs under specific cells are simply moved. Whenplayback is made after recording, playback tones are interrupted at thatportion.

Objects

It is the first object of the present invention to provide aninformation storage medium capable of real-time recording/real-timeplayback of digital moving picture information, and a digitalinformation recording/playback apparatus using this medium.

It is the second object of the present invention to provide aninformation storage medium capable of seamless, continuous playback freefrom any interrupt by managing the access frequency to a scattered orstraggling recorded information group in correspondence with the accessperformance of the playback device (disc drive) used, and a digitalinformation recording/playback apparatus using this medium.

It is the third object of the present invention to provide aninformation storage medium which has special synchronization informationso that video information and audio information can be synchronouslyplayed back (or inter-channel phase synchronization of multi-channelaudio information can be taken) even when the reference clocks of theaudio information have any error, and a digital informationrecording/playback apparatus using this medium.

It is the fourth object of the present invention to provide a digitalinformation recording/playback system which can prevent playbackinformation from being lost (sound interrupt or the like) upon playingback specific information, the recording position of which has beenchanged, when the recording position of the specific information(specific cell) in, e.g., video information, has been changed by, e.g.,an edit process of information recorded on an information storagemedium.

BRIEF SUMMARY OF THE INVENTION

In order to achieve the first object, in an information storage mediumaccording to the present invention, which records and plays back dataincluding video data and control information, the control information(DA21 in FIG. 4; RTR_VMG in FIG. 30) includes information (VOBU entry)that accesses a specific portion (VOBU) of the video data (DA22).

In order to achieve the first object, in an information recording systemaccording to the present invention, which uses an information storagemedium that can record data including video data and controlinformation, information (VOBU entry) for accessing a specific portion(VOBU) of the video data (DA22) is described in the control information(DA21 in FIG. 4; RTR VMG in FIG. 30) recorded on the information storagemedium.

In order to achieve the second object, in an information storage mediumaccording to the present invention, which records a plurality of piecesof video information at discrete positions, the plurality of pieces ofvideo information are recorded to decrease an access frequency to thevideo information to be not more than a predetermined number of timesupon sequentially playing back the plurality of pieces of videoinformation.

In order to achieve the second object, in an information playback systemaccording to the present invention, which plays back recordedinformation from an information storage medium which records a pluralityof pieces of video information at discrete positions, when an accessfrequency to the video information exceeds a predetermined number oftimes upon sequentially playing back the plurality of pieces of videoinformation, recording locations of the plurality of pieces of videoinformation are changed to decrease the access frequency to be not morethan the predetermined number of times.

In order to achieve the third object, in an information storage mediumaccording to the present invention, which records audio/video dataincluding video information, audio information, and control information,the control information describes audio synchronization information(VOBU information/audio synchronization information) for takingsynchronization between the video information and the audio information.

In order to achieve the third object, an information recording/playbacksystem according to the present invention, which records/plays backaudio/video data which includes video information, audio information,and control information on/from a predetermined information storagemedium, describes audio synchronization information (VOBUinformation/audio synchronization information) in the controlinformation, and synchronizes the video information and audioinformation on the basis of the audio synchronization information uponplayback.

In order to achieve the fourth object, in an informationrecording/playback system according to the present invention, whichrecords and plays back audio/video data including video information,audio information, and control information on and from a predeterminedinformation storage medium, audio synchronization information (VOBUinformation/audio synchronization information) is described in thecontrol information, and when specific information in the videoinformation is re-recorded at a different position on the informationstorage medium, audio information that synchronizes the videoinformation is re-recorded at a different position on the informationstorage medium in accordance with the audio synchronization information.

Additional objects and advantages of the invention will be set forth inthe description which follows, and in part will be obvious from thedescription, or may be learned by practice of the invention. The objectsand advantages of the invention may be realized and obtained by means ofthe instrumentalities and combinations particularly pointed outhereinafter.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate presently preferred embodiments ofthe invention, and together with the general description given above andthe detailed description of the preferred embodiments given below, serveto explain the principles of the invention.

FIG. 1 is a view for explaining the structure of arecordable/reproducible optical disc (DVD-RAM/DVD-RW or the like), andthe correspondence between data recorded on the disc and recordingtracks.

FIG. 2 is a view for explaining the structure of a sector included inthe data area shown in FIG. 1.

FIG. 3 is a view for explaining an ECC unit of information included inthe data area shown in FIG. 1.

FIG. 4 is a view for explaining an example of the hierarchical structureof information recorded on the optical disc shown in FIG. 1.

FIG. 5 is a view that exemplifies the correspondence between the cellconfiguration of a video object and program chain PGC in the informationhierarchical structure shown in FIG. 4, and the recorded contents of alead-in area.

FIG. 6 is a view that exemplifies the hierarchical structure ofinformation included in a video object shown in FIG. 5.

FIG. 7 is a view for explaining the contents of a dummy pack shown inFIG. 6.

FIG. 8 is a view that exemplifies the internal structure of cell timeinformation CTI shown in FIG. 4.

FIG. 9 is a view that exemplifies the contents of VOBU information shownin FIG. 8.

FIG. 10 is a view that exemplifies the hierarchical structure ofinformation included in control information DA21 shown in FIG. 4.

FIG. 11 is a view for explaining a case wherein the boundary positionsof video object units VOBU in a cell shown in FIG. 6 deviate from thoseof blocks (a 32-kbyte ECC block is formed by 16 sectors (2 kbytes persector: minimum unit)) that form data in the cell.

FIG. 12 is a view for explaining a case wherein the boundary positionsof video object units VOBU in a cell shown in FIG. 6 match those ofblocks (2 kbytes per sector: minimum unit) that form data in the cell.

FIG. 13 is a view for explaining a case upon playing back cell datarecorded on the disc shown in FIG. 1.

FIG. 14 is a table for explaining an example of the relationship betweencells that form playback data shown in FIG. 13 and program chaininformation.

FIG. 15 is a schematic view of a playback system for explainingcontinuity of a playback signal.

FIG. 16 is a graph for explaining an example of the relationship betweenthe access operations and the like and the temporary storage amount in abuffer memory upon continuously playing back a video signal.

FIG. 17 is a graph for explaining another example (highest accessfrequency) of the relationship between the access operations and thelike and the temporary storage amount in a buffer memory uponcontinuously playing back a video signal.

FIG. 18 is a graph for explaining still another example (the playbacktime balances with the access time) of the relationship between theaccess operations and the like and the temporary storage amount in abuffer memory upon continuously playing back a video signal.

FIG. 19 is a graph for explaining the relationship between the seekdistance and seek time of an optical head.

FIG. 20 is a view for explaining the method of obtaining the averageseek distance of the optical head.

FIG. 21 is a schematic view of a recording system for explainingcontinuity of a recording signal.

FIG. 22 is a view that exemplifies cells which form a part of recordedAV data (video signal information) and a sequence of video object unitsVOBU in each cell.

FIG. 23 is a case wherein cell #2 is edited and data falls short in themiddle of cell #2 (at the position of VOBU 108 e) (VOBU 108 e isre-encoded) in the sequence shown in FIG. 22.

FIG. 24 is a view for explaining changes of the cell configuration, VOBUsequence, and the position of a free area shown in FIG. 22 uponcompletion of editing in FIG. 23.

FIG. 25 is a graph for explaining an example (highest access frequency)of the relationship between the access operations and the like and thetemporary storage amount in a buffer memory upon continuously playingback a video signal.

FIG. 26 is a graph for explaining still another example (the playbacktime balances with the access time) of the relationship between theaccess operations and the like and the temporary storage amount in abuffer memory upon continuously playing back a video signal.

FIG. 27 is a block diagram for explaining the arrangement of a DVD videorecorder which can cope with a synchronization error between video andaudio upon re-arranging (e.g., editing) video information in a videoobject.

FIG. 28 is a block diagram showing the internal arrangement of anencoder and decoder in the arrangement shown in FIG. 27.

FIG. 29 is a flow chart for explaining the synchronization processbetween video and audio in the DVD video recorder shown in FIG. 27.

FIG. 30 is a view for explaining another example of the hierarchicalstructure of information recorded on the optical disc shown in FIG. 1.

FIG. 31 is a view that exemplifies the contents (especially VOBU entryVOBU_ENT#) of time map information TMAPI shown in FIG. 30, and alsoexemplifies the correspondence between the contents and AV data controlinformation DA210 shown in FIG. 4.

FIG. 32 is a view that exemplifies the contents of time map generalinformation TMAP_GI shown in FIG. 31.

FIG. 33 is a view that exemplifies the contents of time entry TM_ENT#shown in FIG. 31.

FIG. 34 is a view for explaining the recorded contents of data area DAin FIG. 30, and a time entry point (access point) upon playing back aspecific portion (e.g., VOBU#3) of the recorded contents.

FIG. 35 is a view for explaining an example of the directory structureof information (data files) recorded on the optical disc shown in FIG. 1to have the structure shown in FIG. 30.

FIG. 36 is a schematic view for explaining a case wherein the cellplayback order of the initially recorded contents (original PGC) hasbeen changed by the user later using a user-defined PGC.

FIG. 37 is a view for explaining problems that will occur in audio datawhen video recording is interrupted before a GOP of MPEG-encoded videodata comes to an end upon recording corresponding audio data togetherwith MPEG-encoded video data.

DETAILED DESCRIPTION OF THE INVENTION

A digital information recording/playback system according to anembodiment of the present invention will be described hereinafter withreference to the accompanying drawings.

As a typical embodiment of a digital information recording/playbacksystem according to the present invention, an apparatus whichrecords/plays back moving picture data encoded based on MPEG2, e.g., aDVD digital video recorder, is known. (A practical example of this DVDdigital video recorder will be explained later.)

FIG. 1 is a view for explaining the structure of recordable optical disc(DVD-RAM/DVD-RW disc or the like) 10 used in the DVD digital videorecorder.

As shown in FIG. 1, this optical disc 10 has a structure obtained byadhering a pair of transparent substrates 14 each having recording layer17 using adhesive layer 20. Each substrate 14 can be formed of a 0.6-mmthick polycarbonate film, and adhesive layer 20 can consist of a verythin (e.g., 40 μm to 70 μm thick) ultraviolet setting resin. When thesepair of 0.6-mm thick substrates 14 are adhered to each other so thattheir recording layers 17 contact each other on the surfaces of adhesivelayer 20, a 1.2-mm thick large-size optical disc 10 is obtained.

Note that each recording layer 17 can have a ROM/RAM double-layeredstructure. In this case, ROM layer/light reflection layer (emboss layer)17A is formed on the side closer to read-out face 19, and RAMlayer/phase change recording layer 17B is formed on the side fartherfrom read-out face 19.

Optical disc 10 has center hole 22, and clamp areas 24 used to clampoptical disc 10 upon its rotation are formed around center hole 22 onthe two surfaces of the disc. Center hole 22 receives the spindle of adisc motor when disc 10 is loaded into a disc drive device (not shown).Optical disc 10 is clamped at its clamp areas 24 by a disc damper (notshown) during disc rotation.

Optical disc 10 has information areas 25 that can record informationsuch as video data, audio data, and the like around clamp areas 24.

In each information area 25, lead-out area 26 is assured on the outerperiphery side. Also, lead-in area 27 is assured on the inner peripheryside of area 25 that contacts clamp area 24. The area between lead-outand lead-in areas 26 and 27 is defined as data recording area 28.

On recording layer (light reflection layer) 17 of information area 25, arecording track is continuously formed in, e.g., a spiral pattern. Thecontinuous track is divided into a plurality of physical sectors, whichhave serial numbers. Various data are recorded on optical disc 10 usingthose sectors as recording units.

Data recording area 28 serves as an actual data recording area, andrecords video data (main picture data) such as a movie or the like,sub-picture data such as superimposed dialogs, menus, and the like, andaudio data such as words, effect sounds, and the like asrecording/playback information in the form of similar pit trains(physical shapes or phase states that bring about optical change inlaser reflected light).

When optical disc 10 is a double-sided recording RAM disc in which eachsurface has one recording layer, each recording layer 17 can be formedby three layers, i.e., by sandwiching a phase-change recording materiallayer (e.g., Ge2Sb2Te5) between two zinc sulfide.silicon oxide(ZnS.SiO2) mixture layers.

When optical disc 10 is a single-sided recording RAM disc in which eachsurface has one recording layer, recording layer 17 on the side ofread-out face 19 can be formed by three layers including theaforementioned phase-change recording material layer. In this case,layer 17 on the side opposite to read-out face 19 need not be aninformation recording layer but may merely be a dummy layer.

When optical disc 10 is a single-sided read type double-layered RAM/ROMdisc, two recording layers 17 can comprise a single phase-changerecording layer (on the side farther from read-out face 19; read/write),and a single semi-transparent metal reflection layer (on the side closerto read-out face 19; read-only).

When optical disc 10 is a write-once DVD-R, a polycarbonate substrate isused, gold can be used as a reflection layer (not shown), and anultraviolet setting resin can be used as a protection layer (not shown).In this case, an organic dye is used in recording layer 17. As theorganic dyes, cyanine, squarilium, chroconic, and triphenylmenthanedyes, xanthene and quinone dyes (naphthoquinone, anthraquinone, and thelike), metal complex dyes (phthalocyanine, porphyrin, dithiol complex,and the like), and so forth can be used.

Data can be written on such DVD-R disc using a semiconductor laserhaving a wavelength of 650 nm and an output of around 6 to 12 mW.

When optical disc 10 is a single-sided read type double-layered ROMdisc, two recording layers 17 can comprise a single metal reflectionlayer (on the side farther from read-out face 19), and a singlesemi-transparent metal reflection layer (on the side closer to read-outface 19).

On read-only DVD-ROM disc 10, pit trains are formed in advance onsubstrate 14 by a stamper, a reflection layer of a metal or the like isformed on the surface of substrate 14 on which the pit trains areformed, and the reflection layer is used as recording layer 17. On suchDVD-ROM disc 10, grooves as recording tracks are not particularlyformed, and the pit trains formed on the surface of substrate 14 serveas tracks.

In various types of optical discs 10 described above, read-only ROMinformation is recorded on recording layer 17 as an embossed patternsignal. By contrast, no such embossed pattern signal is formed onsubstrate 14 having read/write (or write-once) recording layer 17, and acontinuous groove is formed instead. A phase-change recording layer isformed on such groove. In case of a read/write DVD-RAM disc, thephase-change recording layer in land portions is also used forinformation recording in addition to the groove.

When optical disc 10 is of single-sided read type (independently of oneor two recording layers), substrate 14 on the rear side viewed fromread-out face 19 need not always be transparent to the read/write laserbeam used. In this case, a label may be printed on the entire surface ofsubstrate 14 on the rear side.

A DVD digital video recorder (to be described later) can be designed toattain write many/read many (read/write) for a DVD-RAM disc (or DVD-RWdisc), write once/read many for a DVD-R disc, and read many for aDVD-ROM disc.

When disc 10 is a DVD-RAM (or DVD-RW), disc 10 itself is stored incartridge 11 to protect its delicate disc surface. When DVD-RAM disc 10in cartridge 11 is inserted into the disc drive of a DVD video recorder(to be described later), disc 10 is pulled out from cartridge 11, isclamped by the turntable of a spindle motor (not shown), and is rotatedto face an optical head (not shown).

On the other hand, when disc 10 is a DVD-R or DVD-ROM, disc 10 itself isnot stored in cartridge 11, and bare disc 10 is directly set on the disctray of a disc drive.

FIG. 1 also shows the correspondence between data recording area 28 ofoptical disc (DVD-RAM or the like) 10 and recording tracks of datarecorded there.

Recording layer 17 of information area 25 is formed with a continuousdata recording track in a spiral pattern. The continuous track issegmented into a plurality of logical sectors (minimum recording units)each having a given storage size, and data are recorded with referenceto these logical sectors. The recording size per logical sector isdetermined to be 2,048 bytes (or 2 kbytes) which are equal to one packdata length.

Data recording area 28 is an actual data recording area, which similarlyrecords management data, main picture (video) data, sub-picture data,and/or audio data.

Note that data recording area 28 of disc 10 can be segmented into aplurality of ring-shaped (annular) recording areas (a plurality ofrecording zones), although not shown. The disc rotational velocityvaries in units of recording zones. However, within each zone, aconstant linear or angular velocity can be set. In this case, anauxiliary recording area, i.e., spare area (free space) can be providedfor each zone. These free spaces in units of zones may collectively forma reserve area for that disc 10.

The recording signal structure of information recorded on an informationstorage medium (DVD-RAM disc 10 or the like) and the method ofgenerating the recording signal structure will be explained below. Notethat the contents themselves of information recorded on the medium arereferred to as “information”, and a structure or expression obtained byscrambling or modulating information with identical contents, i.e., asequence of “1” and “0” states after signal format conversion, isexpressed as a “signal” to appropriately distinguish them from eachother.

FIG. 2 is a view for explaining the structure of a sector included inthe data area shown in FIG. 1. One sector shown in FIG. 2 corresponds toone of sector numbers of 2,048-byte sectors shown in FIG. 1. Each sectoralternately includes synchronization codes and modulated signals (videodata and the like) to have a header embossed on disc 10.

FIG. 3 is a view for explaining a recording unit (a unit of errorcorrection code ECC) of information included in the data area shown inFIG. 1.

In a FAT (file allocation table) prevalently used in file systems ofinformation storage media (hard disc HDD, magnetooptical disc MO, andthe like) for personal computers, information is recorded on aninformation storage medium to have 256 or 512 bytes as a minimum unit.

By contrast, in information storage media such as a CD-ROM, DVD-ROM,DVD-RAM, and the like, UDF (universal disc format) is used as a filesystem. In this case, information is recorded on an information storagemedium to have 2,048 bytes as a minimum unit. This minimum unit iscalled a sector. That is, each 2,048-byte information is recorded on aninformation storage medium (optical disc 10) using UDF in units ofsectors 501, as shown in FIG. 3.

Since a CD-ROM and DVD-RAM are handled as bare discs without using anycartridge, the surface of an information storage medium is readilyscratched or becomes attached with dust on the user side. For thisreason, a specific sector (e.g., sector 501 c in FIG. 3) cannot often beplayed back (or recorded) due to the influences of dust or scratches onthe information storage medium surface.

DVD adopts error correction (ECC using a product code) in considerationof such situation. More specifically, 16 sectors (16 sectors from sector501 a to sector 501 p in FIG. 3) form one ECC (error correction code)block 502, which has a strong error correction function. As a result,even when an error in ECC block 502 (e.g., sector 501 c is impossible toplay back) has occurred, such error can be corrected, and all pieces ofinformation in ECC block 502 can be correctly played back.

FIG. 4 is a view for explaining an example of the hierarchical structureof information recorded on optical disc (especially, DVD-RAM or DVD-RW)disc 10 shown in FIG. 1.

Lead-in area 27 includes an embossed data zone whose light reflectionsurface has an embossed pattern, a mirror zone whose surface is flat(mirror surface), and a rewritable data zone capable of informationrewrites.

Data recording area (volume space) 28 is comprised of user rewritablevolume/file management information 70, and data area DA.

Data area DA between lead-in and lead-out areas 27 and 26 can recordboth computer data and AV data. The recording order and recordinginformation sizes of computer data and AV data are arbitrary, and anarea where computer data is recorded is named a computer data area (DA1,DA3), and an area where AV data is recorded is named an AV data area(DA2).

Volume/file management information 70 can record information thatpertains to the entire volume, the number of files computer data (dataof a personal computer) and the number of files associated with AV dataincluded in volume space 28, and information that pertains to recordinglayer information and the like.

Especially, the recording layer information can contain:

the number of building layers (for example, two layers in case of asingle ROM/RAM double-layered disc, also two layers in case of a singledouble-layered disc having only a ROM layer, and n layers in case of nsingle-sided, single-layered discs irrespective of ROM or RAM layers);

logical sector number range tables (indicating the size of each layer)assigned in units of layers;

characteristics (a DVD-RAM disc, a RAM portion of a ROM/RAMdouble-layered disc, a DVD-R, CD-ROM, CD-R, and the like) in units oflayers;

assigned logical sector number range tables (including rewritable areasize information in units of layers) in units of zones of a RAM area ofeach layer; and

unique ID information (to find out disc exchange in a multiple discpack) in units of layers.

With the recording layer information including the aforementionedcontents, even a multiple disc pack and a ROM/RAM double-layered disccan be handled as a single, large volume space by setting series logicalsector numbers.

Data area DA records computer data, video data, audio data, and thelike. Volume/file management information 70 records information thatpertains to files of audio/video data recorded on data area DA or theentire volume.

Lead-out area 26 is also capable of information rewrites.

The embossed data zone of lead-in area 27 records, for example, inadvance:

<01> information which pertains to the entire information storagemedium: the disc type (a DVD-ROM, DVD-RAM (or DVD-RW), DVD-R, or thelike); disc size (12 cm, 8 cm, or the like); recording density; physicalsector numbers indicating the recording start/end positions, and thelike;

<02> information which pertains to the recording/playback/erasurecharacteristics: the recording power and recording pulse width; erasepower; playback power; linear velocity upon recording and erasure, andthe like; and

<03> information which pertains to the manufacture of each informationstorage medium: the manufacturing number and the like.

The rewritable zone of each of lead-in area 27 and lead-out area 26, forexample, includes:

<04> a field for recording a unique disc name of each informationstorage medium;

<05> a test recording field (for confirming recording/erasureconditions); and

<06> a field for recording management information that pertains todefective fields in data area DA.

On fields <04> to <06>, a DVD recording apparatus (a dedicated DVD videorecorder, a personal computer installed with a DVD video processingboard and processing software, or the like) can record information.

Data area DA can record audio/video data DA2 and computer data DA1 andDA3 together.

Note that the recording order, recording information size, and the likeof computer data and audio/video data are arbitrary. Data area DA canrecord computer data or audio/video data alone.

Audio/video data area DA2 includes control information DA21, videoobject DA22, picture object DA23, and audio object DA24.

At the first position of audio/video data area DA2, anchor pointer APhaving information that indicates the recording location of controlinformation DA21 is present. When the information recording/playbacksystem uses information in this audio/video data area DA2, the recordinglocation of control information DA21 is checked based on anchor pointerAP, and control information DA21 is read by accessing that location.

Video object DA22 includes information of the contents of recorded videodata.

Picture object DA23 can include still picture information such as stillpictures, slide pictures, thumbnail pictures that represent the contentsof video object DA22 used upon search/edit, and the like.

Audio object DA24 includes information of the contents of recorded audiodata.

Note that recording information of the playback target (contents) ofaudio/video data is included in video object set VOBS shown in FIG. 5(to be described later).

Control information DA21 includes AV data control information DA210,playback control information DA211, recording control information DA212,edit control information DA213, and thumbnail picture controlinformation DA214.

AV data control information DA210 includes information which manages thedata structure in video object DA22 and manages information thatpertains to the recording locations on information storage medium(optical disc or the like) 10, and information CIRWNs indicating thenumber of times of rewrite of control information.

Playback control information DA211 includes control information requiredupon playback, and has a function of designating a sequence of programchains PGC. More specifically, playback control information DA211includes: information that pertains to a playback sequence whichcombines PGCs; information indicating a “pseudo recording location”while considering information storage medium 10 as, e.g., a single tape(digital video cassette DVC or video tape VTR) in association with thatinformation (a sequence for continuously playing back all recordedcells); information that pertains to multi-screen simultaneous playbackhaving different video information contents; search information(information that records corresponding cell IDs and a table of thestart times of cells in units of search categories, and allows the userto select a category to directly access the video information ofinterest); and the like.

With this playback control information DA211, the file name of an AVfile, the path of a directory name, the ID of PGC, and the cell ID canbe designated.

Recording control information DA212 includes control information(programmable timer recording information or the like) required uponrecording (video recording and/or audio recording).

Edit control information DA213 includes control information requiredupon edit. For example, edit control information DA213 can includespecial edit information (EDL information such as corresponding timesetting information, special edit contents, and the like) in units ofPGCs, and file conversion information (information that converts aspecific portion in an AV file, and designates the file storage locationafter conversion, or the like).

Thumbnail picture control information DA214 includes managementinformation that pertains to thumbnail pictures used to search for ascene that the user wants to see in video data or those to be edited,and thumbnail picture data.

Thumbnail picture control information DA214 can include a pictureaddress table, thumbnail picture data, and the like. Thumbnail picturecontrol information DA214 can also include, as lower-layer informationof the picture address table and thumbnail picture data, menu indexinformation, index picture information, slide & still pictureinformation, information picture information, defective areainformation, wallpaper picture information, and the like (not shown).

AV data control information DA210 includes allocation map table AMT,program chain control information PGCCI, and cell time controlinformation CTCI.

Allocation map table AMT includes information that pertains to addresssetups along the actual data allocation, identification ofrecorded/unrecorded areas, and the like on the information storagemedium (optical disc 10 or the like). In the example shown in FIG. 4,allocation map table AMT includes user area allocation descriptor UAD,spare area allocation descriptor SAD, and address conversion table ACT.

Program chain control information PGCCI includes information thatpertains to a video playback program (sequence).

Cell time control information CTCI includes information that pertains tothe data structure of a basic unit (cell) of video information. Thiscell time control information CTCI includes cell time control generalinformation CTCGI, cell time search information CTSI, and m pieces ofcell time search information CTI #1 to CTI #m.

Cell time control general information CTCGI includes information thatpertains to individual cells. Cell time search information CTSI is mapinformation indicating a description position (AV address) ofcorresponding cell time information when a specific cell ID isdesignated.

Each cell time search information (CTI #m) is comprised of cell timegeneral information CTGI #m and cell VOBU table CVT #m. Details of celltime search information (CTI #m) will be explained later with referenceto FIG. 8.

An outline of FIG. 4 has been explained. Supplementary explanations ofthe individual information will be summarized below.

<11> Volume/file management information 70 includes:

information that pertains to entire volume space 28;

the number of files of computer data (DA1, DA3) and audio/video data (AVdata DA2) included in volume space 28;

the recording layer information of the information storage medium(DVD-RAM disc, DVD-ROM disc, or DVD-ROM/RAM multi-layered disc); and thelike.

The recording layer information records:

the number of building layers (example: the number of layers of a singleRAM/ROM double-layered disc is counted as two, that of a single ROMdouble-layered disc is also counted as two, and that of n single-sideddiscs is counted as n);

logical sector number range tables (corresponding to the size of eachlayer) assigned in units of layers;

characteristics (example: a DVD-RAM disc, a RAM portion of a ROM/RAMdouble-layered disc, CD-ROM, CD-R, and the like) in units of layers;

assigned logical sector number range tables (including rewritable areasize information in units of layers) in units of zones of a RAM area ofeach layer;

unique ID information (e.g., to find out disc exchange in a multipledisc pack) in units of layers; and the like. With this information,series logical sector numbers can be set even for a multiple disc packor RAM/ROM double-layered disc to handle it as a single, large volumespace.

<12> Playback control information DA211 records:

information that pertains to a playback sequence which combines PGCs;

“information indicating a pseudo recording location” while consideringinformation storage medium 10 as, e.g., a single tape (digital videocassette DVC or video tape VTR) in association with the playbacksequence that combines PGCs (a sequence for continuously playing backall recorded cells);

information that pertains to multi-screen simultaneous playback havingdifferent video information contents;

search information (information that records corresponding cell IDs anda table of the start times of cells in units of search categories, andallows the user to select a category to directly access the videoinformation of interest); and the like.

<13> Recording control information DA212 records:

programmable timer recording information; and the like.

<14> Edit control information DA213 records:

special edit information (that describes corresponding time settinginformation and special edit contents as an edit library (EDL)) in unitsof PGCs;

file conversion information (information that converts a specificportion in an AV file, and designates the file storage location afterconversion, or the like); and the like.

FIG. 5 exemplifies the correspondence between the cell configuration ofa video object and program chain PGC in the information hierarchicalstructure shown in FIG. 4, and also exemplifies the recorded contents ofthe lead-in area.

In the information hierarchical structure shown in FIG. 5, video objectDA22 is comprised of video object set VOBS. This VOBS has contentscorresponding to one or more program chains PGC#1 to PGC#k whichrespectively designate the cell playback order in different methods.

A video object set (VOBS) is defined as a set of one or more videoobjects (VOB). Video objects VOB in video object set VOBS are used forthe same purpose.

For example, a VOBS for a menu normally consists of one VOB, whichstores a plurality of menu screen display data. By contrast, a VOBS fora title set normally consists of a plurality of VOBs.

Taking a concert video title of a certain rock band as an example, VOBsthat form a video object set (VTSTT_VOBS) for a title set correspond topicture data of the performance of that band. In this case, bydesignating a given VOB, for example, the third tune in the concert ofthat band can be played back.

A VOB that forms video object set VTSM_VOBS for a menu stores menu dataof all the tunes performed in the concert of the band, and a specifictune, e.g., an encore, can be played back according to the menu display.

Note that one VOB can form one VOBS in a normal video program. In thiscase, a single video stream comes to an end in one VOB.

On the other hand, in case of a collection of animations having aplurality of stories or an omnibus movie, a plurality of video streams(a plurality of video chains PGC) can be set in a single VOBS incorrespondence with the respective stories. In this case, the individualvideo streams are stored in corresponding VOBs. An audio stream andsub-picture stream pertaining to each video stream end in thecorresponding VOB.

VOBs are assigned identification numbers (VOB_IDN #i; i=0 to i), andthat VOB can be specified by the identification number. A VOB consistsof one or a plurality of cells. A normal video stream consists of one ora plurality of cells, but a video stream for a menu often consists of asingle cell. Cells are assigned identification numbers (C_IDN#j) likeVOBs.

FIG. 5 also exemplifies the logical structure of information recorded onlead-in area 27 of optical disc 10 shown in FIG. 1.

When disc 10 is set in a DVD video recorder (not shown) (or a DV videoplayer; not shown), information in lead-in area 27 is read first.Lead-in area 27 records a predetermined reference code and control datain ascending order of sector number.

The reference code in lead-in area 27 includes a predetermined pattern(a repetitive pattern of a specific symbol “172”) and consists of twoerror correction code blocks (ECC blocks). Each ECC block has 16sectors. These two ECC blocks (32 sectors) are generated by appendingscramble data. Upon playing back the reference code appended with thescramble data, filter operation or the like on the playback side is doneto play back a specific data symbol (e.g., 172) to assure precision insubsequent data reads.

Control data in lead-in area 27 is made up of 192 ECC blocks. In thiscontrol data field, the contents for 16 sectors in the respective blocksare repetitively recorded 192 times.

FIG. 6 exemplifies the hierarchical structure of information included invideo object DA22 shown in FIG. 5.

As shown in FIG. 6, each cell (for example, cell #m) consists of one ormore video object units (VOBU). Each video object unit is constituted asa set (pack sequence) of video packs, sub-picture packs, and audiopacks.

Each of these packs has a size of 2,048 bytes, and serves as a minimumunit for data transfer. The minimum unit for logical processing is acell, and logical processing is done in units of cells.

The playback time of video object unit VOBU corresponds to that of videodata made up of one or more picture groups (groups of pictures; to beabbreviated as GOPs), and is set to fall within the range from 0.4 secto 1.2 sec. One GOP is screen data which normally has a playback time ofabout 0.5 sec in the MPEG format, and is compressed to play backapproximately 15 frame pictures during this interval.

When video object unit VOBU includes video data, a video datastream isformed by arranging GOPs (complying with MPEG) each consisting of videopacks, sub-picture packs, audio packs, and the like. Also, video objectunit VOBU is defined by one or more GOPs.

Even playback data consisting of audio data and/or sub-picture dataalone is formed using video object unit VOBU as one unit. For example,when video object unit VOBU is formed by audio packs alone, audio packsto be played back in the playback time of video object unit VOBU towhich the audio data belong are stored in that video object unit VOBU asin the video object of video data.

The packs that form each video object unit VOBU have the same datastructure except for a dummy pack. Taking an audio pack as an example,as shown in FIG. 6, a pack header is set at the head of the pack, and apacket header, substream ID, and audio data follow. In such packconfiguration, the packet header is written with information ofpresentation time stamp PTS indicating the head time of the first framein a packet.

With a DVD video recorder that can record video title set VTS (or videoprogram) containing video object DA22 with the structure shown in FIG. 6on optical disc 10, the user often wants to edit the recorded contentsafter this VTS is recorded. In order to meet such requirement, dummypacks can be appropriately inserted in each VOBU. Each dummy pack can beused to record edit data later.

Information that pertains to cells #1 to #m shown in FIG. 6 is recordedin cell time control information CTCI in FIG. 4 and, as shown in FIG. 4,its contents include:

cell time information CTI# 1 to cell time information CTI#m (informationthat pertains to each cell);

cell time search information CTSI (map information indicating adescription position (AV address) of corresponding cell time informationwhen a specific cell ID is designated); and

cell time control general information CTCGI (information that pertainsto the entire cell information).

Each cell time information (e.g., CTI#m) includes cell time generalinformation (CTGI#m) and a cell VOBU table (CVT#m).

The data structure in video object DA22 will be explained below.

A minimum basic unit of video information is called a cell. Data invideo object DA22 is configured as a set of one or more cells #1 to #m,as shown in FIG. 6.

MPEG2 (or MPEG1) is prevalently used as the video informationcompression technique in video object DA22. MPEG segments videoinformation into groups called GOPs in 0.5-sec increments, andcompresses video information in units of GOPs. A video informationcompression unit called video object unit VOBU is formed by one or moreGOPs.

In the present invention, the VOBU size is set to match an integermultiple of ECC block size (32 kbytes) (one of important features of thepresent invention).

Furthermore, each VOBU is segmented into packs in units of 2,048 bytes,and these packs record raw video information (video data), audioinformation (audio data), sub-picture information (superimposed dialogdata, menu data, and the like), dummy information and the like. Theseare recorded in the form of video packs, audio packs, sub-picture packs,and dummy packs.

Note that the dummy pack is inserted for the purposes of:

addition of information to be additionally recorded after videorecording (for example, memo information indicating that postrecordinginformation is inserted into an audio pack and is replaced by a dummypack is inserted in a sub-picture pack as sub-picture information and isreplaced by a dummy pack);

compensating for a size that is short from an integer multiple of 32kbytes to adjust the VOBU size just to an integer multiple of ECC blocksize (32 kbytes); and the like.

In each pack, a pack header and packet header (and substream ID) are setbefore object data (audio data in case of, e.g., an audio pack).

In the DVD video format, an audio pack and sub-picture pack include thesubstream ID between the packet header and object data.

In the packet header, a time code for time management is recorded.Taking an audio packet as an example, PTS (presentation time stamp)information that records the head time of the first audio frame in thatpacket is inserted in the form shown in FIG. 6.

FIG. 7 shows the structure of the contents (for one dummy pack) of thedummy pack shown in FIG. 6. That is, one dummy pack 89 is comprised ofpack header 891, packet header 892 having a predetermined stream ID, andpadding data 893 padded with a predetermined code (insignificant data).(Packet header 892 and padding data 893 form padding packet 890). Thecontents of padding data 893 of an unused dummy pack do not have anyspecial meaning.

This dummy pack 89 can be used as needed when the recorded contents areedited after predetermined recording is done on disc 10 shown in FIG. 1.Also, dummy pack 89 can be used to store thumbnail picture data, whichis used for a user menu. Furthermore, dummy pack 89 can be used for thepurpose of matching each VOBU size in AV data DA2 with an integermultiple of 32 kbytes (32-kbyte align).

For example, a case will be examined below wherein the contents of avideo tape that recorded a family trip using a portable video camera arerecorded and edited on DVD-RAM (or DVD-RW) disc 10.

In this case, only the video scenes to be stored in a single disc areselectively recorded on disc 10. These video scenes are recorded in avideo pack in FIG. 6. Also, audio data simultaneously recorded by thevideo camera is recorded in an audio pack.

Each VOBU that includes these video pack, audio pack, and the like canhave a navigation pack (not shown), which is adopted in DVD video, atits beginning, as needed.

This navigation pack contains playback or presentation controlinformation PCI and data search information DSI. Using this PCI or DSI,the playback procedure of each VOBU can be controlled (for example,discontinuous scenes can be automatically connected or a multianglescene can be recorded).

Alternatively, each VOBU may have a synchronization navigation pack(SNV_PCK; not shown) which simply has synchronization information inunits of VOBUs without having contents as complex as those of anavigation pack of DVD video.

Note that a DVD video RAM assumes a case without using any navigationpack currently. However, a DVD-R may use a navigation pack.

After the contents of the video tape are edited and recorded on disc 10,when a voice, effect sound, and the like are to be postrecorded in eachscene in units of VOBUs or background music BGM is added, suchpostrecorded audio data or BGM can be recorded in dummy pack 89. When acomment for the recorded contents is to be added, sub-pictures such asadditional characters, figures, and the like can be recorded in dummypack 89. Furthermore, when an additional video picture is to beinserted, the inserted video picture can be recorded in dummy pack 89.

The above-mentioned postrecorded audio data or the like is written inpadding data 893 of dummy pack 89 used as an audio pack. The additionalcomment is written in padding data 893 of dummy pack 89 used as asub-picture pack. Similarly, the inserted video picture is written inpadding data 893 of dummy pack 89 used as a video pack.

Furthermore, when each VOBU size including the recorded/edited packsequence does not match an integer multiple of ECC block size (32kbytes), dummy pack 89 which includes as padding data 893 insignificantdata that can match this VOBU size with an integer multiple of 32 kbytescan be inserted into each VOBU.

In this manner, by appropriately inserting a dummy pack (padding pack)into each recorded/edited VOBU to match each VOBU size with an integermultiple of ECC block size (the aforementioned 32-kbyte align), allVOBUs can be always be rewritten in units of ECC blocks.

Alternatively, when 32-kbyte align is done, if a RAM layer of disc 10has suffered a defect, only the defect portion can be replaced in unitsof ECC blocks. Furthermore, when the ECC block unit is used as theaddress unit of AV data, each VOBU address can be easily converted.

That is, dummy pack 89 is a wildcard pack that can become any of audio,sub-picture, and video packs depending on its purpose.

FIG. 8 is a view for explaining the internal structure of cell timeinformation CTI shown in FIG. 4.

As has been explained in the description of FIG. 4, each cell timesearch information (CTI#m) is made up of cell time general informationCTGI#m and cell VOBU table CVT#m.

As shown in the upper half of FIG. 8, the cell time general informationincludes:

(1) cell data general information;

(2) a time code table;

(3) acquired defect information;

(4) cell video information;

(5) cell audio information; and

(6) cell sub-picture information.

Cell data general information (1) contains a cell ID, the total timeduration of that cell, the number of cell data sets (extents), a celldata set descriptor, a cell time physical size, and the number ofconstituent VOBUs of that cell.

Note that the cell ID is a unique ID in units of cells. The total timeduration indicates the total time required for playing back that cell.

The number of cell data sets (number of extents) indicate the number ofcell data set descriptors in that cell.

The description contents of the cell data set descriptor (cell dataextent descriptor) will be explained below.

Assume that a recording information cluster, which pertains to a singlecell in the layout order of ECC blocks that can be used is one cell dataset (cell data extent). In this case, specific cell #1 is considered asone cell data set unless it is divided by another cell #2.

As an example of a description method, the length (the number of ECCblocks where a cell data set is recorded) of the cell data set isexpressed by “2 bytes”, the start address (AV address) of the cell dataset is expressed by “3 bytes”, and they are described at neighboringpositions. For example, we have:

Cell data set descriptor (the number of ECC blocks, startaddress)=CED(*,*)

A statement that describes all cell data sets that form one cell is acell data set descriptor. With this descriptor, the distribution of allAV addresses where cells are recorded can be determined, thus allowingeasy access.

Since the lengths of cell data sets and the start AV addresses of celldata sets are described in pairs, when many continuously recorded areasare formed on information storage medium 10, the number of bytesrequired for describing the cell data set descriptor decreases, the datasize required for the cell time general information (#m) decreases, andthe recording size that can be used for video object DA22 can berelatively increased accordingly.

Note that corresponding AV addresses viewed along the layout ofinformation storage medium 10 are often arranged in a discontinuousorder. However, since allocation map table AMT shown in FIG. 4 isavailable, the recording locations of all data in a given cell on theinformation storage medium can be specified by the start AV address inthe cell data set descriptor.

In FIG. 8, the cell time physical size indicates a recording locationsize on the information storage medium where a cell including aninherent defect location is recorded. By combining this cell timephysical size and the total time duration, the size of an inherentdefective area in a given cell can be detected, and a practical transferor transmission rate can be expected. This cell time physical size canbe used to determine a recording location candidate of a cell that canguarantee continuous playback.

The number of constituent VOBUs indicates the number of VOBUs thatconstitute that cell.

Time code table (2) includes information of the number of pictures inVOBUs #1 to #n which form the cell, and information of the number of ECCblocks in VOBUs #1 to #n which form the cell (as shown in FIG. 3, sinceone ECC block=16 sectors, the information of the number of ECC blockscan also be expressed by information of the number of sectors).

A time code in this table is expressed by a pair of the number ofpictures (the number of video frames; expressed by 1 byte) in units ofVOBUs in the cell of interest, and the number of used ECC blocks(expressed by 1 byte) in units of VOBUs at the recording location on themedium indicated by the cell data set descriptor. Using this expressionmethod, the time code can be recorded in a very small information size(compared to a case wherein time codes are appended to each of 30 framesper sec in NTSC).

Acquired defect information (3) includes the number of acquired defectsin that cell, and information of the addresses of the acquired defects.

The number of acquired defects indicates the number of ECC blocks thathave suffered acquired defects in that cell. The acquired defect addressindicates the location of each acquired defect by an AV address in unitsof ECC blocks. Every time a defect is produced upon cell playback (i.e.,ECC error correction fails), the AV address of the defective ECC blockis registered as the acquired defect address.

Cell video information (4) includes information such as the type ofvideo information (NTSC, PAL, or the like) of that cell, a compressionmethod (MPEG2, MPEG1, motion JPEG, or the like), a stream ID andsubstream ID (main screen or sub screen; used in multi-screensimultaneous recording/playback), a maximum transmission rate, and thelike.

Cell audio information (5) includes information such as the type of anaudio signal (linear PCM, MPEG1, MPEG2, Dolby AC-3, or the like), asampling frequency (48 kHz or 96 kHz), the number of quantization bits(16 bits, 20 bits, or 24 bits), and the like.

Cell sub-picture information (6) includes the number of sub-picturestreams in each cell and information indicating their recordinglocations.

On the other hand, the cell VOBU table includes VOBU information #1 toVOBU information #n which form that cell, as shown in the lower half ofFIG. 8. Each VOBU information includes VOBU general information, dummypack information, and audio synchronization information.

The individual information contents in the cell time information (CTI#m)in FIG. 8 can be summarized as follows:

(11) cell data general information (general information that pertains toeach cell and includes the following contents);

-   -   (11.1) cell ID (unique identifier for each cell)    -   (11.2) total time duration (total required time required for        playing back cell contents)    -   (11.3) the number of cell data sets (the number of cell data set        descriptors in a cell)    -   (11.4) cell data set descriptor    -   (11.5) cell time physical size (which indicates the recording        location size on the information storage medium where a cell        including an inherent defect location is recorded. By combining        with the aforementioned “total time duration”, the size of an        inherent defective area in the cell can be determined, and a        practical transmission rate can be expected. This information is        used to “determine a recording location candidate of a cell that        can guarantee continuous playback”.)    -   (11.6) the number of constituent VOBUs (the number of VOBUs that        constitute a cell)

(12) time code table;

(13) acquired defect information (acquired defect information detectedin a cell, which includes the following contents);

-   -   (13.1) the number of acquired defects (the number of ECC blocks        in which acquired defects that have suffered acquired defects in        a cell)    -   (13.2) acquired defect address (which indicates the location of        acquired defect by an AV address value in units of ECC blocks.        The address value is registered as needed every time a defect is        produced upon playback of a cell.)

(14) cell video information (including the following contents);

-   -   (14.1) video signal type (NTSC or PAL)    -   (14.2) compression method (MPEG2, MPEG1, or motion JPEG)    -   (14.3) stream ID and substream ID information (main screen or        sub screen R used in multi-screen simultaneous        recording/playback)    -   (14.4) maximum transmission rate

(15) cell audio information (including the following contents);

-   -   (15.1) signal type (linear PCM, MPEG1, MPEG2, or Dolby AC-3)    -   (15.2) sampling frequency    -   (15.3) the number of quantization bits

(16) cell sub-picture information (which indicates the number of streamsof sub-picture information in each call and their recording locations.)

The aforementioned “time code table” is expressed by pairs of thenumbers (the numbers of frames: expressed by 1 byte) #1 to #n ofpictures in units of VOBUs in a cell, and the numbers (expressed by 1byte) of used ECC blocks in units of VOBUs at the recording locations onthe information storage medium indicated by the “cell data setdescriptor”, as indicated in the upper portion in FIG. 8.

Using this expression method, the time code can be recorded with a verysmall information size.

An access method using this time code will be explained below.

1. A video recording/playback application designates the cell ID to beaccessed and its time;

2. the video management layer detects the picture number (frame number)of the corresponding picture (video frame) from the cell start positionon the basis of the designated time;

3. the video management layer computes by sequentially summing up thenumber of pictures (the number of frames) in units of VOBUs from thehead of the cell shown in FIG. 8 to detect a picture number (framenumber) and VOBU number from the head to which the picture (frame)designated by the video recording/playback application corresponds;

4. the recording locations of all data in the cell on the informationstorage medium are detected from the cell data set descriptor shown inFIG. 8 and allocation map table AMT shown in FIG. 4;

5. the values of the numbers (#1 to #n) of ECC blocks of VOBUs (#n) inFIG. 8 are summed up to the VOBU number (#n) detected in item “3.”above, and the AV address at the corresponding VOBU start position ischecked;

6. the corresponding VOBU start position is directly accessed on thebasis of the result in item “5.” above to trace until the predeterminedpicture (frame) obtained in item “3.” above is reached; and

7. at this time, when I-picture recording end position information inthe VOBU to be accessed is required, I-picture end position informationin FIG. 9 is used.

FIG. 9 is a view for explaining the internal structure of the cell VOBUtable (VOBU information) shown in FIG. 8.

Time management information (presentation time stamp PTS) that pertainsto audio information is recorded in a packet header, as shown in FIG. 6.In order to extract this information (PTS), information of an audio packmust be directly played back. However, since the audio pack is recordedat a location deep inside the management layer, editing of videoinformation in units of cells becomes time-consuming.

To combat this problem of “time-consuming editing in units of cells” andthe like, synchronization information for audio information is providedin AV data control information DA210 in FIG. 4. This synchronizationinformation is audio synchronization information shown in FIG. 9.

Referring to FIG. 9, VOBU general information indicates the end positionof I-picture of MPEG-encoded video information, and is expressed by adifferential address from the start position of a VOBU at the lastposition of I-picture (1 byte).

Dummy pack information is expressed by the number of dummy packs (1byte) indicating the number of dummy packs (FIG. 7) inserted intorespective VOBUs, and the dummy pack distribution (dummy pack numbers×2bytes) including the differential address from the start position of agiven VOBU to the dummy pack insertion position (2 bytes) and theindividual numbers of dummy packs (2 bytes).

Audio synchronization information is expressed by an audio streamchannel number (1 byte) indicating the number of channels of an audiostream, I-picture audio positions #1, #2, . . . (1 byte each; the mostsignificant bit designates the direction of a position including anotherconcurrent audio pack . . . “0”=backward, “1”=forward), each of whichindicates the differential address value of an ECC block that includesan audio pack of the same time as the I-picture start time from the headof a VOBU, I-picture start audio sample numbers #1, #2, . . . (2 byteseach), each of which indicates the sample number of the audio sampleposition of the same time as the I-picture start time in a given ECCblock as a coefficient of serial numbers of all audio packs, audiosynchronization information flags #1, #2, . . . (1 byte each), each ofwhich indicates the presence/absence of synchronization informationbetween audio and video streams, and audio synchronization data (2bytes) which is appended to each audio synchronization information flagonly when the audio synchronization information flag indicates the“presence of synchronization information”, and indicates the number ofaudio samples included in a corresponding VOBU.

Each of I-picture start audio positions #1, #2, . . . in FIG. 9indicates the differential address value of an ECC block that includesan audio pack of the same time as the I-picture start time from the headof the corresponding VOBU.

Furthermore, I-picture start audio positions #1, #2, . . . in FIG. 9indicate the audio sample positions of the same time as the I-picturestart time as counts of serial numbers of all audio packs.

For example, upon dividing AV information in a given cell in videoediting, when a VOBU in that cell is divided into two VOBUs and eachdivided information is re-encoded, division free from any interrupt ofplayback tones and any phase shift between playback channels can beimplemented using the aforementioned information (I-picture start audioposition #1 and I-picture start audio sample number #1) in FIG. 9.

An example of this point will be explained below.

The frequency shift of the reference clocks of a normal digital audiorecorder is approximately 0.1%. When sound source information digitallyrecorded by a digital video tape (DAT) recorder is overdubbed on videoinformation already recorded on a DVD-RAM disc by digital copy, thereference clocks between the video information and audio information mayhave an error of around 0.1%. Such reference clock error becomes solarge that it cannot be ignored upon repeating the digital copy (ornonlinear edit using a personal computer or the like), and appears asinterrupted playback tones or a phase shift between playback channels.

In an embodiment of the present invention, synchronization informationcan be recorded as an option to synchronously play back videoinformation and audio information (or to attain phase synchronizationamong channels of multi-channel audio data) even when the referenceclocks of audio information have shifted.

More specifically, in the audio synchronization information in FIG. 9,the presence/absence of synchronization information between audio andvideo streams can be set in units of audio stream IDs (#1, #2, . . . ).

When this audio synchronization information is present, the number ofaudio samples is described in units of VOBUs in audio synchronizationdata in that information. Using this information (the number of audiosamples), synchronization between video information and audioinformation or synchronization between channels of multi-channel audiodata can be attained in units of VOBUs in each audio stream uponplayback.

FIG. 10 exemplifies the hierarchical structure of information includedin control information DA21 in FIG. 4.

Each cell in FIG. 5 or 6 indicates a playback period that designatesplayback data by its start and end addresses. On the other hand, programchain PGC in FIG. 5 is a series of playback execution units thatdesignate the playback order of cells. Playback of video object set VOBSin FIG. 5 is determined by program chains PGC and cells that form videoobject set VOBS.

AV data control information DA210 in FIG. 10 has control informationPGCCI of such program chain PGC. This PGC control information PGCCI ismade up of PGC information management information PGC_MAI, k (one ormore) PGC information search pointers, and k (one or more) pieces of PGCinformation, the number of which is equal to that of the PGC informationsearch pointers.

PGC information management information PGC_MAI includes informationindicating the number of PGCs. Each PGC information search pointerpoints to the head of each PGC information PGCI, and allows easy searchfor corresponding PGC information PGCI.

Each PGC information PGCI includes PGC general information and m piecesof cell playback information. This PGC general information includes aPGC playback time and the number of pieces of cell playback information.

Problems posed when the position of a sector as a minimum unit ofaddress has deviated from that of video object unit VOBU shown in FIG. 6will be explained below with reference to FIG. 11.

When new information is recorded on a data change area in FIG. 11 orinformation there is updated, complicated processes which:

1) play back an ECC block present at the start position of VOBU#g;

2) deinterleave the ECC block;

3) change information of a portion that pertains to the data change areain the ECC block;

4) re-assign error correction codes in the ECC block; and

5) overwrite changed information at the ECC block position are required.As a consequence, a continuous recording process in NTSC video recordingthat requires a frame rate of 30 frames per sec is disturbed.

Furthermore, when the surface of an information storage medium (DVD-RAMdisc 10) has dust or scratches, a recording process is influenced moreseriously by such dust or scratches than a playback process.

More specifically, when dust or scratches are present near that positionof an ECC block which includes a sector that is to undergo processes 1)to 5) above, VOBU#g has been played back without any problem so far, butan information defect is produced by a rewrite process of the ECC blockincluding that sector, and it may become impossible to play back VOBU#g.

Also, every time information is rewritten in a data change area which isnot relevant to VOBU#g, the start position of VOBU#g is required. Aphase change recording film used as the recording material of theDVD-RAM disc has a tendency that its characteristics deteriorate afterrepetitive recording and defects increase. Hence, it is preferable tominimize the number of times of rewrite of a portion which need not berewritten (the start position of VOBU#g in FIG. 11) (the number of timesof rewrite can be recorded in control information rewrite count CIRWNsin FIG. 4).

For these reasons, in order to guarantee a continuous recording processat a frame rate of 30 frames per sec, to minimize the number of times ofrewrite of unwanted portions, and so forth, in the present invention,the VOBU recording unit is set to match an integer multiple of ECC blocksize (32 kbytes), as shown in FIG. 6 (note that 2 kbytes of a sector areused as a minimum unit of address). This process is called 32-kbytealign.

To attain 32-kbyte align, i.e., to set each VOBU size to always match aninteger multiple of 32 kbytes before and after data change, a dummy pack(FIG. 7) having an appropriate size is inserted into each VOBU.

A method of setting an AV address number set based on the aforementionedcondition (32-kbyte align that sets the recording unit to match aninteger multiple of ECC block size) will be explained below compared toanother logical block number assignment method.

In order to allow easy conversion to logical block numbers used in thefile system, losses or repetitions of numbers due to replace processesfor defects produced on information storage medium 10 are avoided.

Upon recording video information, a replace process is done for a defecton the information storage medium. At this time, the setting location ofan AV address moves on information storage medium 10 as a result of thisreplace process.

Let “AVA” be the AV address number, “LBN” be the logical block number,and “LBNav” be the logical block number at the AV file start position.Then, the logical block number and AV address number satisfy:

AVA=(LBN−LBNav)÷16

Note that digits after the decimal point of the quotient obtained upondivision by 16 are dropped.

FIG. 12 shows a case wherein the 32-kbyte align is executed by insertinga dummy pack into a cell whose data has been changed after videorecording. Then, the boundary positions of video object units VOBU inthe cell match those of ECC blocks (32 kbytes) which form data in thatcell.

As a result, upon rewriting data later, data can be overwritten in unitsof ECC blocks (ECC need not be re-encoded). In addition, when the AVaddress uses an ECC block made up of 16 sectors as a unit, addressmanagement is easy even when overwrite (insert edit or the like) is madeafter video recording. Since this overwrite is made irrespective ofVOBU#g who data has not changed, playback of data of VOBU#g never failsdue to rewrite of the data change area.

When each VOBU size matches an integer multiple of 32 kbytes before andafter data change even when no dummy pack is inserted (an integermultiple of 32 kbytes also means that of 2 kbytes of a sector), no dummypack need be added for the purpose of the 32-kbyte align. However, sincethe dummy pack can be used in addition to 32-kbyte align (e.g., as anauxiliary area for postrecording and the like), an appropriate number ofdummy packs are preferably inserted irrespective of 32-kbyte align.

FIG. 13 shows an example of playback of cell data recorded on disc 10shown in FIG. 1.

As shown in FIG. 13, playback data is designated by a playback periodfrom cell A to cell F. A playback combination of these cells in eachprogram chain (PGC) is defined by program chain information.

FIG. 14 is a table for explaining an example of the relationship betweencells that form playback data shown in FIG. 13, and program chaininformation (PGCI) (see FIG. 5).

More specifically, PGC#1 comprised of three cells #1 to #3 designatescell playback in the order of cell A→cell B→cell C. PGC #2 comprised ofthree cells #1 to #3 designates cell playback in the order of cellD→cell E→cell F. Furthermore, PGC#3 comprised of five cells #1 to #5designates cell playback in the order of cell E→cell A→cell D→cellB→cell E.

In FIGS. 13 and 14, PGC#1 exemplifies a continuous playback period fromcell A to cell C, and PGC#2 exemplifies an intermittent playback periodfrom cell D to cell F. On the other hand, PGC#3 shows an example thatallows discontinuous cell playback independently of the cell playbackdirection and repetitive playback (cells C and D).

<Method of Assuring Continuous Playback Condition>

An indispensable condition for video information is to guaranteecontinuity upon playback unlike conventional computer information. Asinformation for guaranteeing continuous playback, neither a special flagnor a statement are required. Information that guarantees continuityupon playback can be recorded in PGC control information PGCCI shown inFIG. 4. More specifically, “information that guarantees continuity uponplayback” can be inserted in the form of adding a predeterminedcondition to a PGC coupling method that couples cells. Insertion of thepredetermined condition will be explained below.

FIG. 15 is a schematic view of a playback system to explain continuityof a playback signal.

Video information recorded on information storage medium 10 is read byoptical head 202, and is temporarily saved in buffer memory(semiconductor memory) 219. The video information read out from thisbuffer memory 219 is sent externally. The transmission rate of the videoinformation sent from optical head 202 to buffer 219 will be referred toas a physical transmission rate (PTR) hereinafter. Also, the averagevalue of the transmission rate of the video information externallytransferred from buffer memory 219 is named a system transmission rate(STR). In general, physical and system transmission rates PTR and STRassume different values.

In order to play back information recorded at different locations oninformation storage medium 10 in turn, access operation for moving thefocused spot position of optical head 202 is required. Seek access formoving entire optical head 202 is made to attain large movement; jumpaccess for moving only an objective lens (not shown) for focusing laseris made to attain a movement for a very small distance.

FIG. 16 shows a change over time in video information amount temporarilysaved in buffer memory 219 upon externally transferring videoinformation while making access control.

In general, since system transmission rate STR is higher than physicaltransmission rate PTR, the video information amount temporarily saved inbuffer memory 219 continues to increase during the period of a videoinformation time. When the temporarily saved video information amounthas reached the capacity of buffer memory 219, a playback process byoptical head 202 is intermittently done, and the video informationamount temporarily saved in buffer memory 219 maintains the buffermemory capacity full state (corresponding to a flat top of the graph inthe video information playback time in FIG. 16).

When video information recorded at another location on informationstorage medium 10 is to be played back successively, an access processof optical head 202 is executed.

Three different access periods of optical head 202, i.e., a seek accesstime, a jump access time, and a rotation wait time of informationstorage medium 10, are required, as shown in FIG. 16. In these periods,since no information is played back from information storage medium 10,physical transmission rate PTR during these periods is substantially“0”. By contrast, since average system transmission rate of videoinformation to be externally sent remains constant, the videoinformation temporary saved amount in buffer memory 219 keeps ondecreasing (a graph that declines to the right during the seek accesstime, jump access time, or rotation wait time in FIG. 16).

Upon completion of access of optical head 202, when playback frominformation storage medium 10 restarts (smaller one of the hatched videoinformation playback times in FIG. 16), the video information temporarysaved amount in buffer memory 219 increases again.

This increase slope is determined by the difference between the physicaltransmission rate and average system transmission rate, i.e., (physicaltransmission rate PTR)−(average system transmission rate STR).

After that, when access is made again near the playback position oninformation storage medium 10, since it can be attained by only jumpaccess, only the jump access time and rotation wait time are required (agraph that declines to the right in FIG. 16).

A condition that allows continuous playback in the playback operationshown in FIG. 16 can be defined by the “upper limit value of an accesscount during a specific period”. That is, the information contents ofPGC control information PGCCI shown in FIG. 4, e.g., a cell combinationshown in FIG. 14, are set so that the access count assumes a value equalto or smaller than the “upper limit value of an access count during aspecific period”.

An access count condition that absolutely disables continuous playbackwill be explained below using FIG. 17.

When the access frequency is highest, the video information playbacktime is very short, as shown on the right side of the graph center inFIG. 17, and only the jump access time and rotation wait timesuccessively appear. In such case, it is impossible to assure playbackcontinuity irrespective of physical transmission rate PTR.

Let BM be the size of buffer memory 219. Then, the temporary saved videoinformation in buffer memory 219 is exhausted within a period:

BM/STR(=BM÷STR)   (01)

and continuous playback is disabled.

Let JATi (Jump Access Time of an objective lens) be each jump accesstime, and MWTi (Spindle Motor Wait Time) be each rotation wait time.Then, in the example shown in FIG. 17, we have:

BM/STR=Σ(JATi+MWTi)   (02)

Approximating equation (02), and letting JATa be the average jump accesstime, MWTa be the average rotation wait time, and n be the access countwithin the period until the temporary saved video information in buffermemory 219 is exhausted, equation (02) can be rewritten as:

BM/STR=n·(JATa+MWTa)   (03)

In this case, an indispensable condition as “access count n untiltemporary saved video information in buffer memory 219 is exhausted”which is an absolute condition for assuring continuous playback is:

n<BM/(STR·(JATa+MWTa))   (04)

The value given by inequality (04) is rewritten to access count N persec as:

N=n/(BM/STR)<1/(JATa+MWTa)   (05)

Since average system transmission rate STR when MPEG2 is used is around4 Mbps (bits per second), and the average rotation cycle of a 2.6-GBDVD-RAM single-sided, single-layered disc is approximately 35 ms(milliseconds), average rotation wait time MWTa is MWTa≈18 ms. On theother hand, a general information recording/playback apparatus hasJATa≈5 ms.

As a practical example of size BM of the buffer memory 219, some driveswith a larger size have 2 Mbytes=16 Mbits, but the buffer memory sizesof most drives (information recording/playback apparatuses) is around512 kbytes=4 Mbits in the status quo (in terms of the product cost).

Upon computing using buffer memory size BM=4 Mbits, the shortest timeuntil the temporary saved video information in buffer memory 219 isexhausted is 4 Mbits/4 Mbps≈1 sec. Substituting this value in inequality(04) yields:

n<BM/(STR·(JATa+MWTa))=1 sec/(18 ms+5 ms)≈43

A computation example under the specified condition yields theaforementioned result (access count upper limit n≈43). However, sincethe computation result changes depending on the buffer memory size andaverage system transmission rate of the apparatus, equation (03) servesas a condition formula required to assure continuous playback.

When access is made at an access frequency slightly lower than thatobtained by equation (03), and when physical transmission rate PTR ismuch higher than average system transmission rate STR, continuousplayback is enabled.

In order to allow continuous playback by satisfying only the conditionof equation (03), the following prerequisites must be satisfied:

1) physical transmission rate PTR is extremely high; and

2) all pieces of video information to be accessed are allocated atnearby locations and can be accessed by only jump access without anyseek access.

Hence, a condition that can guarantee continuous playback even whenphysical transmission rate PTR is relatively low will be examined below.

As shown in FIG. 18, when the video information playback time and accesstimes have good balance, and the temporary saved video information inbuffer memory 219 is maintained nearly constant from a global point ofview, continuity of video information playback viewed from an externalsystem can be assured without exhausting temporary saved videoinformation in buffer memory 219.

Let SATi (Seek Access Time of an objective lens) be each seek accesstime, SATa be the average seek access time after n accesses, DRTi (DataRead Time) be the playback information read time per access, and DTRa bethe average playback information read time after n accesses.

Then, the data amount externally transferred from buffer memory 219during the total access period of n accesses is given by:

STR×(Σ(SATi+JATi+MWTi))≈STR×n×(SATa+JATa+MWTa)   (06)

When the value given by equation (06) and the video information amount:

(PTR−STR)×ΣDRTi≈(PTR−STR)×n·DRTa   (07)

stored in buffer memory 219 upon playing back video information by naccesses satisfy (PTR−STR)×n·DRTa≧STR×n×(SATa+JATa+MWTa), i.e.,

(PTR−STR)·DRTa≧STR·(SATa+JATa+MWTa)   (08)

continuity of playback video viewed from the external system side can beassured.

If N represents the average access count per sec, we have:

1≈N·(DRTa+SATa+JATa+MWTa)   (09)

From formulas (08) and (09), since

1/(N·(SATa+JATa+MWTa)≧1+STR/(PTR−STR)

solving this inequality for N yields:

N<1/{[1+STR/(PTR−STR)](SATa+JATa+MWTa)}  (10)

N of this inequality (10) defines the access count upper limit value persec that can assure continuity of playback video.

The relationship between the seek access distance and the seek accesstime required therefor will be examined below.

FIG. 19 is a view for explaining the relationship between the seekdistance and seek time of an optical head.

When a target position has been reached while accelerating/deceleratingat equal acceleration α, the moving distance until time tmax at whichthe moving speed of optical head 202 becomes maximum is α·tmax·tmax/2from FIG. 19. Hence, total distance ρ the optical head has moved by seekaccess is given by:

ρ=α·tmax tmax   (11)

As can be seen from equation (11), the time required for seek access isproportional to the ½-th power (i.e., a square root) of the movingdistance.

FIG. 20 is a view for explaining the average seek distance of theoptical head.

The average seek distance (average seek access distance) upon recordingvideo information on an area having radial width L will be examined. Asshown in FIG. 20, the average seek distance from a position distance X0from the end (of a seek area) to all recording areas is given by:

X0X0/2L+(L−X0)·(L−X0)/2L   (12)

When the average value upon moving X0 from 0 to L is computed usingformula (12), the average seek distance as a result of integrating X0under prescribed conditions is:

L/3   (13)

A case will be examined below wherein an area corresponding to half theradial width on optical disc 10 which corresponds to data area DA shownin FIG. 4 is used to record AV data area DA2.

In this case, from formula (13) the average seek distance (average seekaccess distance) is ⅙ the radial width on optical disc 10 correspondingto data area DA.

For example, when optical head 202 takes 0.5 sec to move (seek) from theinnermost periphery to the outermost periphery of the recording area(data area DA in FIG. 4), from equation (11) the average seek time(average seek access time) within AV data area DA2 is:

SATa≈200 ms   (14)

which is a value proportional to the ½-th power of ⅙ of 0.5 sec.

For example, MWTa≈18 ms and JATa≈5 ms are used in computations, asdescribed above. In such case, a 2.6-GB DVD-RAM disc has PTR=11.08 Mbps.When the average transmission rate of MPEG2 is STR≈4 Mbps, if theaforementioned values are substituted in inequality (10), N≦2.9 isobtained.

FIG. 21 is a schematic view of a recording system to explain continuityof a recording signal.

Recording information is externally sent to buffer memory 219 at averagesystem transmission rate STR (around 4 Mbps in MPEG2 video). Buffermemory 219 temporarily holds the sent information (MPEG video data andthe like), and transfers the held information to optical head 202 atphysical transmission rate PRT that matches the storage medium and thetype of drive.

In order to record the information at different locations on informationstorage medium 10 in turn, access operation that moves the focused spotposition of optical head 202 is required. Seek access for moving entireoptical head 202 is made to attain large movement; jump access formoving only an objective lens (not shown) for focusing laser is made toattain a movement for a very small distance.

<Access Frequency Reduction Method; Re-Arrange Cells by Editing>

FIG. 22 exemplifies cells that form a portion of recorded AV data (videosignal information), and video object unit VOBU sequences of therespective cells.

FIG. 23 is a view for explaining a case wherein cell #2 is edited anddata falls short in the middle of cell #2 (at the position of VOBU 108e) in the sequence shown in FIG. 22 (VOBU 108 e is re-encoded).

Furthermore, FIG. 24 is a view for explaining changes in cellconfiguration, VOBU sequences, and position of a free area exemplifiedin FIG. 22 upon completion of edit in FIG. 23.

In order to guarantee the seamless, continuous playback or recording,each cell layout in PGC information (FIGS. 10 and 14) in PGC controlinformation PGCCI in FIG. 4 is set to satisfy the condition of formula(5) or (10). However, when the access frequency becomes higher than aseamless guarantee value due to user requests in the edit operation, theaccess frequency reduction process is executed again to satisfy theconditions of formulas (03) or (08).

This re-process will be explained below.

Assume that the cell playback order:

cell #1→cell #2→cell #3

is initially set, as shown in FIG. 22 (in this case, no access occursduring playback).

Then, the user divides cell #2 into cell #2A and cell #2B (FIG. 23), andsets the cell playback order:

cell #2A→cell #1→cell #2B→cell #3

In this case, the access count increases by two, that is:

access from the end of cell #2A to the head of cell #1; and

access from the end of cell #1 to the head of cell #2B.

In this manner, when formula (03) or (08) cannot be satisfied as aresult of an increase in access count in that PGC, cell #2A is moved tofree area 107, as shown in FIG. 24.

As a result, the access count in the PGC that defines the playback order“cell #2A→cell #1→cell #2B→cell #3” decreases to one, that is:

access from the end of cell #1 to the head of cell #2B.

As in the above example, when formula (03) or (08) cannot be satisfied,some cells are moved (to change the recording location on informationstorage medium 10), thus lowering the access frequency. In this way,formula (03) or (08) is satisfied to guarantee seamless, continuousplayback or recording in that PGC.

When formula (03) or (08) is not satisfied even after an increase inaccess count due to editing is decreased by the aforementioned method,the user re-checks the cell configuration of the PGC to re-configure thenumber and sequence (layout) of cells in the PGC so as to satisfyformula (03) or (08).

<Method of Assuring Continuous Recording Condition>

FIG. 25 is a graph for explaining an example of the relationship betweenaccess operations and the temporary saved amount in the buffer memoryupon continuous recording of a video signal (when the access frequencyis highest). FIG. 26 is a graph for explaining another example of therelationship between access operations and the temporary saved amount inthe buffer memory upon continuous recording of a video signal (when therecording time and access time have good balance).

Unlike in the “case wherein continuous playback is disabled when thetemporary saved video information amount on buffer memory 219 isexhausted” that has been explained with reference to FIG. 17, thetemporary saved video information amount on buffer memory 219 issaturated upon continuous recording, as shown in FIG. 25.

More specifically, as can be seen from a comparison between FIGS. 25 and17, formula (03) can be applied to the access frequency that satisfiesthe continuous recording condition.

Likewise, as can be seen from a comparison between FIGS. 26 and 18,formula (08) can be applied to the access frequency that satisfies thecontinuous recording condition.

According to the “conditional formula for assuring continuity” that hasbeen explained with reference to FIGS. 16 to 20 and FIGS. 25 and 26,seamless, continuous playback or recording (free from any interruptduring playback or recording) can be guaranteed irrespective of thecharacteristics of an information recording/playback apparatus (drive)used.

FIG. 27 is a block diagram for explaining the arrangement of a DVD videorecorder which can cope with a synchronization error between video andaudio upon re-arranging (e.g., editing) video information in a videoobject.

The apparatus main body of the DVD video recorder shown in FIG. 27 isroughly constructed by disc drive 32 for rotating DVD-RAM (DVD-RW) disc10, and reading/writing information to/from disc 10, disc changer (ordisc pack) 100 which automatically supplies predetermined disc 10 todisc drive 32, and can load a plurality of discs 10, encoder 50 on thevideo recording side, decoder 60 on the playback side, and main MPU 30for controlling the operations of the apparatus main body.

Data processor 36 can have functions of supplying DVD recording dataoutput from encoder 50 to disc drive 32, receiving a DVD playback signalplayed back from disc 10 via drive 32, rewriting management informationrecorded on disc 10, and erasing data recorded on disc 10, under thecontrol of main MPU 30.

Also, data processor 36 forms ECC groups by combining packs sent fromformatter 56 in units of 16 packs, appends error correction informationto each ECC group, and sends these ECC groups to disc drive 32. In thiscase, when disc drive 32 is not ready to record on disc 10, ECC groupdata appended with error correction information are transferred totemporary storage 34, and are temporarily stored therein until drive 32is ready to record. When disc drive 32 is ready to record, recording ofdata stored in temporary storage 34 on disc 10 starts.

Main MPU 30 includes a ROM written with control programs and the like, aRAM that provides a work area required for executing a program, an audioinformation synchronization processor, a telephone I/F or Internet I/F,and the like.

MPU 30 executes an audio information synchronization process (to bedescribed later; FIG. 29) and other processes using its RAM as a workarea in accordance with the control programs stored in its ROM.

Of the execution results of main MPU 30, the contents that the DVD videorecorder user is informed of are displayed on a display unit (not shown)of the DVD video recorder, or are displayed on a monitor display (notshown) in an on-screen display (OSD) mode.

The information recording/playback apparatus portion that writes/reads(records and/or plays back) information to/from DVD disc 10 comprisesdisc changer (disc pack) 100, disc drive 32, temporary storage 34, dataprocessor 36, and system time counter (or system time clock; STC) 38.

Temporary storage 34 is used to buffer a predetermined amount of data ofthose to be written in disc 10 via disc drive 32 (i.e., data output fromencoder 50), and to buffer a predetermined amount of data of thoseplayed back from disc 10 via disc drive 32 (i.e., data input to decoder60). In this sense, temporary storage 34 in FIG. 27 has a functioncorresponding to buffer memory 219 in FIG. 21.

For example, when temporary storage 34 is comprised of a semiconductormemory (DRAM) of 4 to 8 Mbytes, it can buffer recording or playback datafor approximately 8 to 16 sec at an average recording rate of 4 Mbps. Onthe other hand, when temporary storage 34 is comprised of a 16-MbyteEEPROM (flash memory), it can buffer recording or playback data forapproximately 32 sec at an average recording rate of 4 Mbps.Furthermore, when temporary storage 34 is comprised of a 100-Mbyte verycompact HDD (hard disc), it can buffer recording or playback data for 3min or more at an average recording rate of 4 Mbps.

When the DVD video recorder has an external card slot (not shown in FIG.27), the EEPROM may be sold as an optional IC card. On the other hand,when the DVD video recorder has an external drive slot or SCSIinterface, the HDD can be sold as an optional expansion drive.

In this connection, in an embodiment (not shown) in which a DVD videorecorder is implemented by software using personal computer PC, the freespace of a hard disc drive or a main memory of PC itself can bepartially used as temporary storage 34 in FIG. 27.

Temporary storage 34 can also be used to temporarily store recordinginformation until disc 10 is exchanged by a new one, when disc 10 hasbeen fully recorded during video recording, in addition to theaforementioned purpose of guaranteeing “seamless, continuous playback orrecording”.

Furthermore, when disc drive 32 uses a high-speed drive (double-speed orhigher), temporary storage 34 can be used to temporarily store data thatexcesses data to be read out from a normal drive within a predeterminedperiod of time.

When read data upon playback is buffered on temporary storage 34, evenwhen an optical pickup (not shown) produces read errors due to avibration shock or the like, playback data buffered on temporary storage34 can be used instead, thus preventing the played back picture frombeing interrupted.

As an analog signal source of a raw signal to be recorded on disc 10, avideo playback signal of VHS video, laser disc LD, or the like isavailable, and this analog video signal is input to encoder 50 via an AVinput shown in FIG. 27.

As another analog signal source, normal analog TV broadcast (ground orsatellite broadcast) is available, and this analog TV signal is input toencoder 50 from a TV tuner shown in FIG. 27 (in case of TV, textinformation such as closed caption or the like is often broadcastedsimultaneously with video information, and such text information is alsoinput to encoder 50).

As a digital signal source of a raw signal to be recorded on disc 10, adigital output or the like of a digital broadcast tuner is available,and this digital video signal is directly input to encoder 50.

When this digital tuner has an IEEE1394 interface or SCSI interface, itssignal line is connected to main MPU 30.

When a bitstream (including MPEG-encoded video) of DVD video isdigitally broadcasted directly, and the digital tuner has a digitaloutput of the bitstream, since the bitstream output has already beenencoded, it is directly transferred to data processor 36.

Note that the analog video output of a digital device which does nothave any digital video output but has digital audio output (e.g.,digital video cassette DVC or digital VHS video DVHS) is connected tothe Av input, and its digital audio output is supplied to encoder 50 viasample rate converter SRC. This SRC converts a digital audio signalhaving a sampling frequency of, e.g., 44.1 kHz into that having asampling frequency of 48 kHz.

Although no signal lines are illustrated in FIG. 27, when personalcomputer PC can output a digital video signal in the DVD video format,that digital video signal can be directly input to encoder 50.

All digital input audio signal sources (digital tuner, DVC, DVHS, PC,and the like) are connected to main MPU 30. This is done to use suchsignals in the “audio synchronization process” to be described later.

The control timings that main MPU 30 controls disc changer (disc pack)100, disc drive 32, data processor 36, and encoder 50 and/or decoder 60can be determined based on time data output from STC 38 (videorecording/playback operations are normally done in synchronism with timeclocks from STC 38, but other processes may be executed at timingsindependently of STC 38).

A DVD digital playback signal which is played back from disc 10 via discdrive 32 is input to decoder 60 via data processor 36.

As will be described in detail later using FIG. 28, decoder 60 includesa video decoder for decoding a main picture video signal from the inputDVD digital playback signal, a sub-picture decoder for playing back asub-picture signal from this playback signal, an audio decoder forplaying back an audio signal from this playback signal, a videoprocessor for compositing the decoded sub-picture on the decoded mainpicture, and a means (reference clock generator) for correcting timingerrors between video and audio signals or among channels of amulti-channel audio signal.

A video signal (main picture +sub-picture) decoded by decoder 60 issupplied to video mixer 602. Video mixer 602 receives reduced-scalepicture/thumbnail picture data (see FIG. 4) and text data from main MPU30 as needed. This thumbnail picture (and/or text) are/is composited onthe decoded video signal on frame memory 604 to generate a visual menu(user menu) used in a recorded content search and the like.

When thumbnail pictures for the user menu are displayed on a monitor(not shown a thumbnail picture file previously saved as an independentfile is flowed as stream packs, and is displayed by designating displaypositions (X- and Y-coordinate values) in frame memory 604. At thistime, if text data or the like is included, text is displayed below eachthumbnail picture using a character ROM (or kanji ROM).

A digital video signal including this visual menu (user menu) as neededis output outside the apparatus shown in FIG. 27 via a digital videoI/F. Also, the digital video signal including the visual menu as neededis converted into an analog video signal via a video DAC, and the analogvideo signal is sent to an external analog monitor (a TV with an AVinput).

Note that thumbnail picture data for the user menu may be inserted intorecording data as independent video pack data in place of theaforementioned independent file. That is, the DVD video format specifies“0” (stream ID=0E0h) as a stream number for main picture data, and canalso specify “1” (stream ID=0E1h) as that for thumbnail picture data andmultiplex such stream. The multiplexed thumbnail pictures with thestream number=“1” serve as source data used in a menu edit process.

FIG. 28 is a block diagram for explaining the internal arrangement ofthe encoder and decoder in the arrangement shown in FIG. 27.

Encoder 50 comprises ADC (analog-to-digital converter) 52, video encoder53, audio encoder 54, sub-picture encoder 55, formatter 56, buffermemory 57, frame memory 51 for thumbnail pictures, thumbnail videoencoder 58, and memory 59 used upon encoding thumbnail pictures.

ADC 52 receives an external analog video signal+external analog audiosignal from the AV input in FIG. 27, or an analog TV signal+analog audiosignal from the TV tuner. ADC 52 converts the input analog video signalinto a digital signal at a sampling frequency of, e.g., 13.5 MHz/6.75MHz and 8 quantization bits.

That is, luminance component Y is converted into digital data at asampling frequency of 13.5 MHz and 8 quantization bits, and colordifference components Cr (or Y-R) and Cb (or Y-B) are respectivelyconverted into digital data at a sampling frequency of 6.75 MHz and 8quantization bits.

Similarly, ADC 52 converts the input analog audio signal into a digitalsignal at a sampling frequency of, e.g., 48 kHz and 16 quantizationbits.

When an analog video signal and digital audio signal are input to ADC52, the digital audio signal passes through ADC 52. (The digital audiosignal may undergo processes for reducing jitter alone, changing thesampling rate or the number of quantization bits, and the like withoutchanging its contents.)

On the other hand, when a digital video signal and digital audio signalare input to ADC 52, these signals pass through ADC 52 (these signalsmay also undergo a jitter reduction, sampling rate change process, andthe like without changing their contents).

A digital video signal component output from ADC 52 is supplied toformatter 56 via video encoder 53. Also, a digital audio signalcomponent output from ADC 52 is supplied to formatter 56 via audioencoder 54.

Video encoder 53 has a function of converting the input digital videosignal into a digital signal compressed at a variable bit rate by MPEG2or MPEG1.

Audio encoder 54 has a function of converting the input digital audiosignal into a digital signal compressed at a fixed bit rate (or linearPCM digital signal) by MPEG or AC-3.

When a DVD video signal is input from the AV input or when a DVD videosignal (digital bitstream) is broadcasted and received by TV tuner 44, asub-picture signal component (sub-picture pack) in the DVD video signalis sent to sub-picture encoder 55. Alternatively, if a DVD video playerwith a sub-picture signal independent output terminal is available, asub-picture signal component can be extracted from that sub-pictureoutput terminal. Sub-picture data input to sub-picture encoder 55 isarranged into a predetermined signal format, and is then supplied toformatter 56.

Formatter 56 performs predetermined signal processes for the input videosignal, audio signal, sub-picture signal, and the like while usingbuffer memory 57 as a work area, and outputs recording data that matchesa predetermined format (file structure) to data processor 36.

The respective encoders (53 to 55) compress and packetize the inputsignals (video, audio, and sub-picture). (Note that packets aresegmented and packetized to have a size of 2,048 bytes per pack.) Thesecompressed signals are input to formatter 56. Formatter 56 determinesand records presentation time stamp PTS and decoding time stamp DTS ofeach packet in accordance with the timer value from STC 38 as needed.

In this case, packets of thumbnail pictures used in the user menu aretransferred to and temporarily saved in memory 59 for storing thumbnailpictures. The thumbnail picture packet data is recorded as anindependent file upon completion of video recording. The size of eachthumbnail picture on the user menu is selected to be, e.g.,approximately 144 pixels×96 pixels.

Note that MPEG2 compression, which is the same as the compression formatof main picture data, can be used as that of thumbnail pictures, butother compression schemes may be used. For example, other compressionschemes such as JPEG compression, runlength compression (pallet=256colors: requires a reduction to 256 colors), TIFF format, PICT format,and the like can be used.

Formatter 56 temporarily saves packet data in buffer memory 57, thenpacks the input packet data to mix them in units of GOPs of MPEG, andtransfers the packs to data processor 36.

The contents of standard encoding for generating the recording data tobe transferred to data processor 36 will be briefly explained below.

When encoder 50 starts encoding, parameters required for encoding video(main picture) data and audio data are set. The main picture data ispre-encoded using the set parameters to compute an optimal code amountdistribution to a predetermined average transmission rate (recordingrate). Based on the code amount distribution obtained by pre-encoding,the main picture data is encoded. At this time, the audio data isencoded at the same time.

As a result of pre-encoding, when data compression is insufficient (whena desired video program cannot be stored in a DVD-RAM or DVD-R disc usedto record data), if pre-encoding can be done again (for example, if therecording source is the one capable of read many such as a video tape,video disc, or the like), the main picture data is partially re-encoded,and the re-encoded main picture data portion replaces the previouslypre-encoded main picture data portion. With a series of such processes,the main picture data and audio data are encoded, and the average bitrate value required for recording is reduced largely.

Likewise, parameters required for encoding the sub-picture data are set,and encoded sub-picture data is generated.

The encoded main picture data, audio data, and sub-picture data arecombined and converted into a data structure for video recording.

That is, the configuration of cells that construct program chain PGCshown in FIG. 5 or 14, attributes of main picture, sub-picture, andaudio data, and the like are set (some pieces of such attributeinformation use information obtained upon encoding the individual data),and information management table information containing various kinds ofinformation is created.

The encoded main picture data, audio data, and sub-picture data aresegmented into packs each having a predetermined size (2,048 bytes), asshown in FIG. 6. Dummy packs (FIG. 7) are inserted into these packs asneeded to implement the aforementioned “32-kbyte align”.

Packs other than the dummy packs describe time stamps such as a PTS(presentation time stamp; see FIG. 6), DTS (decoding time stamp), andthe like as needed. As for the PTS of sub-picture data, a timearbitrarily delayed from that of main picture data or audio data in thesame playback time zone can be described.

The data cells are arranged in units of VOBUs so as to play back data inthe order of their time codes, thus formatting a VOBS constructed by aplurality of cells, as shown in FIG. 5, as video object DA22.

When a DVD playback signal is digitally copied from a DVD video player,since the contents of cells, program chain, management tables, timestamps, and the like are predetermined, they need not be generatedagain. (When a DVD video recorder is designed to digitally copy a DVDplayback signal, copyright protection means such as digital watermarkingor the like must be taken.)

Decoder 60 in FIG. 28 comprises: reference clock generator 61 forgenerating sync-locked reference clocks on the basis of audiosynchronization signal A-SYNC sent from main MPU 30 in FIG. 27;separator 62 for separating and extracting packs from playback data withthe structure shown in FIG. 6; memory 63 used upon signal processes suchas pack separation and the like; video decoder 64 for decoding mainpicture data (the contents of a video pack) separated by separator 62;sub-picture decoder 65 for decoding sub-picture data (the contents of asub-picture pack) separated by separator 62; video processor 66 forcompositing sub-picture data output from sub-picture decoder 65 withvideo data output from video decoder 64, as needed, and outputting mainpicture data with superimposed sub-picture data such as menus, highlightbuttons, superimposed dialog, and the like; audio decoder 68 fordecoding audio data (the contents of an audio pack) separated byseparator 62 at the timing of the reference clock from reference clockgenerator 61; a digital audio I/F for externally outputting a digitalaudio signal from audio decoder 68; and a DAC for converting the digitalaudio signal from audio decoder 68 into an analog audio signal, andexternally outputting the analog audio signal.

The analog audio signal from this DAC is supplied to external components(not shown; a multichannel stereophonic apparatus having two to sixchannels).

Note that audio synchronization signal A-SYNC is used to synchronizeaudio signals in units of, e.g., VOBUs shown in FIG. 6.

Main MPU 30 in FIG. 27 can generate audio synchronization signal A-SYNCby detecting audio synchronization packs, when a digital audio signalsent from a digital input device includes the configuration shown inFIG. 6 and the audio synchronization packs (SNV_PCK; not shown) areinserted at the head positions of respective VOBUs.

Alternatively, main MPU 30 in FIG. 27 can generate audio synchronizationsignal A-SYNC using PTS information obtained by detecting presentationtime stamps PTS (FIG. 6) included in audio packs.

In the arrangement shown in FIGS. 27 and 28, the data processes uponplayback are done as follows.

Upon receiving a playback start command by user's operation, main MPU 30loads the management area of disc 10 from disc drive 32 via dataprocessor 36, and determines the address to be played back(corresponding to the address using common logical sector number LSN).

Main MPU 30 then sends the previously determined address of playbackdata and a read command to disc drive 32.

An MPU (not shown) in disc drive 32 reads out sector data from disc 10in accordance with the received command, and data processor 36 makeserror correction of the readout data and sends the data to decoder 60 inthe form of pack data.

In decoder 60, the readout pack data are packetized. Then, video packetdata (MPEG video data) is transferred to video decoder 64, audio packetdata to audio decoder 68, and sub-picture packet data to sub-picturedecoder 65 in correspondence with the data purposes.

At the beginning of transfer of these packet data, presentation timestamp PTS is loaded to STC 38. After that, the respective decoders indecoder 60 execute playback processes in synchronism with the PTS valuein packet data (while comparing PTS and STC values), thus displaying amoving picture with audio and superimposed dialog on a TV monitor (notshown).

By setting the aforementioned AV address, video information in aplurality of DVD-ROM and/or DVD-RAM discs inserted into a multiple discpack (disc changer 100 in FIG. 27) can be loaded as a part of an AVfile.

In a DVD video (DVD-ROM) disc, the recording location of a video objectis set by a logical block number (or a logical or physical sectornumber) as a file entry. In this case, when address conversion table ACTshown in FIG. 4 is used, this logical block number can be converted intothe AV address. This address conversion table ACT describes pairs oflogical block numbers and AV addresses on a table.

FIG. 29 is a flow chart for explaining a synchronization process betweenvideo and audio in the DVD video recorder shown in FIG. 27.

A video signal input from the AV input such as a TV tuner, VTR, camerarecorder, or the like is converted into a digital signal by ADC 52 (stepST200).

The converted digital signal is separated into video information andaudio information, which are individually encoded by video encoder 53and audio encoder 54. Closed caption information or information sent assuperimposed text of teletext is encoded by sub-picture encoder 55 assub-picture data. The encoded video information, audio information, andsub-picture information are respectively inserted in video, audio, andsub-picture packs in units of 2,048 bytes by formatter 56, and thesepacks are arranged in units of VOBUs having a size corresponding to aninteger multiple of 32 kbytes, as shown in FIG. 6 (step ST202).

At this time, formatter 56 extracts information indicating “the sampleposition of the audio information sample position at the I-picturedisplay start time at the head of a VOBU and how many packs this audiopack goes back (or ahead) with reference to the position of a videopack” (step ST204A).

The extracted audio information sample position information is sent tomain MPU 30 in FIG. 27.

The audio information synchronization processor in main MPU 30 sendsback to formatter 56 a signal for generating presentation time stamp PTSor synchronization navigation pack SNV_PCK (not shown) as a source ofaudio synchronization signal A-SYNC on the basis of the received audioinformation sample position information.

Formatter 56 sends VOBU information shown in FIG. 6, which includes thesource information (PTS or SNV_PCK) of audio synchronization signalA-SYNC together with the encoded video information, sub-pictureinformation, and audio information, to data processor 36. Parallel to“audio information sample position information extraction step ST204A”which is then repeated, data processor 36 records video object DA22consisting of VOBU information shown in FIG. 6 at the designated address(AV address) of disc 10 (step ST204B).

As the recording progresses, disc drive 32 returns address information(logical sector number LSN) used in recording to main MPU 30. Main MPU30 computes the recording location on disc 10 (e.g., the physical sectornumber PSN position on disc 10 of an audio information sample at theI-picture display start position at the head position of a givenrecorded VOBU) on the basis of the returned address information and thecorrespondence between the predetermined and sector. This computationresult is used in step ST208 later.

The recording location on disc 10 (the physical sector number PSNposition on disc 10 of an audio information sample at the I-picturedisplay start position at the head position of a given VOBU) correspondsto “I-picture audio positions #1, #2, . . . ” included in audiosynchronization information shown in FIG. 9. That is, the differentialaddress value of an ECC block that includes an audio pack of the sametime as the I-picture audio position I-picture start time shown in FIG.9 is recorded using 1 byte. Of 1 byte, whether the audio sample positionis located before or after the head position of a given VOBU isidentified using the most significant bit. More specifically,

Most significant bit=0: located before VOBU

Most significant bit=1: located after VOBU

Recording of video object DA22 on disc 10 proceeds until a recording endinput is detected (for example, until the user instructs to stoprecording or until the free area of disc 10 is used up) (NO in stepST206; ST200 to ST204A/ST204B).

If the recording end input is detected (YES in step ST206), informationthat pertains to recording such as the recording end address (physicalsector number PSN on disc 10), the recording date/time, and the like iswritten in the management area (control information DA21) on disc 10(step ST208). At this time, upon writing information in the managementarea, control information rewrite count CIRWNs shown in FIG. 4 isincremented by 1.

Note that a value that counts the sample number in an ECC block at theaudio sample position of the same time as the I-picture start time usingserial numbers of all audio packs is written in the management area(control information DA21) as “I-picture start audio sample numbers #1,#2, . . . ” included in the audio synchronization information shown inFIG. 9 (step ST208).

Note that the recording location on disc 10 need not always be expressedby the AV address in units of ECC blocks (16 sectors). The “recordinglocation on disc 10” can also be expressed using the logical blocknumber, logical sector number, or physical sector number as the AVaddress.

<Edit Process of Cell Including Audio Synchronization Information inFIG. 9>

A case will be examined below wherein cell #2 in information recorded ondisc 10 in the order of cell #1, cell #2, and cell #3, as shown in FIG.22, is divided into cells #2A and #2B, as shown in FIG. 23, cell #2A ismoved to free area 91, as shown in FIG. 24, and re-arranged cells areplayed back in the order of:

cell #2A→cell #1→cell #2B→cell #3

In this case, VOBU 108 e is re-encoded, and is divided into VOBUs 108 pand 108 q. The audio information synchronization processor in main MPU30 searches for the position of an audio pack included in cell #2A to bemoved on the basis of the I-picture audio position (FIG. 9) andI-picture audio sample number (FIG. 9) from disc 10.

If the audio pack included in cell #2 is present in either VOBU 108 e or108 q, the corresponding audio pack is extracted therefrom, and isembedded in VOBU 108 d* or 108 p.

In this case, if that VOBU has an extra dummy pack (having nosignificant recording data), the audio pack is embedded in such dummypack. If no such dummy pack is available, re-arrangement of the formatand re-encoding in some cases are done.

On the other hand, when cell #2A includes an audio pack used by VOBU 108c or 108 f, the corresponding audio pack is copied from cell #2A, and isinserted (embedded) in VOBU 108 c or 108 f. At this time, the insertion(embedding) result is recorded in the I-picture audio position andI-picture start audio sample number (FIG. 9). A series of operationcontrol processes are mainly executed by the audio informationsynchronization processor in main MPU 30 in FIG. 27.

A case will be explained below wherein existing audio information from adigital audio information storage medium such as a CD, MD, or the likeis overdubbed as background music on video information afterplayback/editing mentioned above.

A method of overdubbing audio information includes a method of replacingdummy packs in FIGS. 6 and 7 by audio packs, and a method of re-encodingaudio information to be overdubbed.

In some cases, the sampling frequency (32 kHz or 44.1 kHz) of audioinformation is different from that (48 kHz or 96 kHz) of audioinformation in the recorded video information. Even when the nominalfrequency remains the same, the frequency drift (fluctuation offrequency) of a quartz oscillator that generates the reference frequencyis normally around ±0.1%. Therefore, when digital audio information isdigitally dubbed, recording is done at different reference frequencies.As a consequence, when data is played back at the frequency oforiginally recorded audio frequency, a synchronization error occurs.

In order to prevent such error, in the present invention, the number ofaudio samples in units of VOBUs for the digitally dubbed audioinformation can be recorded as an option in the management area (controlinformation DA21 in FIG. 4).

More specifically, as shown in audio synchronization flags #1, #2, . . .in FIG. 9, a flag indicating whether or not audio synchronization datais recorded is set for each audio stream number, and when the audiosynchronization data is to be recorded (flag is set), the number ofaudio samples of each VOBU is expressed by 2 bytes in the audiosynchronization information in FIG. 9.

This audio synchronization information can be recorded as follows.

Audio information to be overdubbed is converted into audio packs inunits of 2,048 bytes by formatter 56 in FIG. 28. At this time, the audioinformation synchronization processor in main MPU 30 in FIG. 27 sendsinformation as to required times in units of VOBUs of the videoinformation of interest. Based on that time information, formatter 56replies the numbers of audio samples in units of VOBUs to the audioinformation synchronization processor.

Then, audio packs including the audio information to be overdubbed arereplaced by dummy packs, thus completing video object DA22.

After that, based on the numbers of audio samples in units of VOBUsreplied from formatter 56 to main MPU 30, the audio informationsynchronization processor records required information in the audiosynchronization information on disc 10.

Upon playback, the audio information synchronization processor in mainMPU 30 reads the audio synchronization information on disc 10, and sendsthe numbers of audio samples in units of VOBUs to reference clockgenerator 61 in the form of “audio synchronization signal A-SYNC”.Reference clock generator 61 generates reference clocks with thefrequency adjusted (sync-locked) to that information (A-SYNC), and audiodecoder 68 plays back post-inserted audio information (overdubbed audioinformation) in synchronism with video information in correspondencewith the frequency of the generated reference clocks.

In this manner, audio playback free from any synchronization errors fromvideo information can be implemented.

In the above description, the numbers of audio samples are recorded inunits of VOBUs. However, the present invention is not limited to this,and the numbers of audio samples may be recorded in units of cells or inunits of video frames (or video fields).

According to the aforementioned embodiment, the following effects areobtained:

A) video information can be re-arranged while guaranteeingsynchronization of an audio signal;

B) even when digital audio information generated at a sample frequencydifferent from that of an original is recorded in dummy packs or thelike by a digital dubbing process after video recording, audioinformation can be synchronously played back; and

C) even when multi-channel audio information of, e.g., AC-3 isre-arranged or mix-down edit from digital sources having differentsampling frequencies is done, synchronization among channels can beguaranteed.

In the above description, a DVD-RAM disc has been exemplified as aninformation storage medium. Alternatively, the system of the presentinvention (especially, a system that performs address management andreplace processes in units of 32-kbyte ECC blocks; or a system thatperforms address management and replace processes in units of 2-kbytesectors) can be applied to a system which uses a file allocation table(FAT) for a personal computer in a file system using a magnetoopticaldisc (MO disc) as an information storage medium.

As system software (or operating system), NTFS (New Technology FileSystem), UNIX, and the like can be used in addition to MS Windows. Morespecifically, required system software (one or a plurality of kinds ofoperating systems OS), application software, and the like are recordedas an embossed pattern on ROM layer 17A in a ROM/RAM double-layereddisc, the OS and directory information of ROM layer 17A are copied to amain memory of a personal computer in a recording/playback process, andthe application software stored in ROM layer 17A can be directly used.In this case, since the application software need not be mapped on themain memory, the main memory space can be broadened. In such personalcomputer system, RAM layer 17B of identical disc 10 can be used as alarge-size storage medium for saving the operation result (edited videoand the like) of the application software in ROM layer 17A.

Furthermore, the AV addresses in units of ECC blocks have been explainedas the addresses of the AV data structure. Alternatively, the addressesof AV data can be managed using, e.g., addresses in units of 2,048-bytesectors.

FIG. 30 is a view for explaining another example of the hierarchicalstructure of information recorded on the optical disc shown in FIG. 1.

The recorded contents of data area DA correspond to those shown in FIG.4 that has already been explained.

More specifically, the recorded contents of audio/video data area DA2 inFIG. 30 correspond to those of audio/video data area DA2 shown in FIG. 4as follows:

navigation data (RTR_VMG) DA21 a in FIG. 30 . . . control informationDA21 in FIG. 4;

movie video object (RTR_MOV.VOB) DA22 a in FIG. 30 . . . video objectDA22 in FIG. 4;

still picture video object (RTR_STO.VOB) DA23 a in FIG. 30 . . . pictureobject DA23 in FIG. 4;

additional audio object (RTR_STA.VOB) DA24 a for still pictures in FIG.30 . . . audio object DA24 in FIG. 4;

manufacturer specification object (MSP.VOB) DA25 a in FIG. 30 . . . notshown in FIG. 4; and

another stream object (AST.SOB) DA26 a in FIG. 30 . . . not shown inFIG. 4.

Note that RTR is an abbreviation for real-time recording.

Navigation data (RTR_VMG) DA21 a is used upon controlling recording,playback, and editing of an AV stream (one or more video objects VOBs).This RTR_VMG has all required navigation data as well as a singlemanagement information file called RTR.IFO.

More specifically, navigation data (RTR_VMG) DA21 a includes RTR videomanagement information (RTR VMGI) DA210 a, movie AV file informationtable (M_AVFIT) DA210 b, still picture AV file information table(S_AVFIT) DA210 c, original PGC information (ORG PGCI) DA210 d,user-defined PGC information table (UD_PGCI) DA210 e, text data manager(TXTDT_MG) DA210 f, and manufacturer information table (MN_FIT) DA210 g.

Those pieces of information (DA210 a to DA210 g) are successivelyrecorded in file RTR.IFO in the aforementioned order.

Most of information described in this file RTR.IFO is stored in a systemmemory (work RAM in MPU 30 in FIG. 27).

RTR VMGI/DA210 a describes basic information (information similar tovideo manager information VMGI in a DVD video ROM) of an RTR disc (disc10 in FIG. 1).

M_AVFIT_SA/DA210 b describes a movie AV file corresponding toRTR_MOV.VRO in FIG. 35 (VRO is an abbreviation for a video recorderobject).

In correspondence with AV data control information DA210 in controlinformation DA21 in FIG. 4, navigation data DA21 a in FIG. 30 includesmovie AV file information table (M_AVFIT) DA210 b.

This movie AV file information table (M_AVFIT) DA210 b includes movie AVfile information table information (M_AVFITI) DA2100, one or more piecesof movie VOB stream information (M_VOB_STI#1 to M_VOB_STI#n) DA2102-1 toDA2102-n, and movie AV file information (M_AVFI) DA2104.

M_AVFI/DA2104 describes information of a movie AV file having a filename “RTR_MOV.VRO”.

This movie AV file information (M_AVFI) DA2104 includes movie AV fileinformation general information (M_AVFI_GI) DA21040, one or more movieVOB information search pointer #1 to #n (MVOBISRP#1 to M_VOBI_SRP#n)DA21042-1 to DA21042-n, and one or more pieces of movie VOB information#1 to #n (M_VOBI#1 to MVOBI#n) DA21044-1 to DA21044-n.

n pieces of M_VOBI in M_AVFI/DA2104 are described in the same order asthat of VOB data stored in the movie AV file.

Each movie VOB information (e.g., M_VOBI#n/DA21044-n) includes movie VOBgeneral information M_VOBI_GI and time map information TMAPI.

FIG. 31 exemplifies the contents of time map information TMAPI in FIG.30, and also the correspondence between these contents and AV datacontrol information DA210 in FIG. 4.

Time map information TMAPI is used upon executing special playback(e.g., cell playback in the order unique to each user using user definedPGC) and time search.

Time map information TMAPI includes time map general informationTMAP_GI, one or more time entries TM_ENT#1 to TM_ENT#r, and one or moreVOBU entries VOBU_ENT#1 to VOBU_ENT#q.

Each VOBU entry contains information of the size and playback time ofeach VOBU. The VOBU size is presented in units of sectors (2 kbytes),and the playback time is presented in units of video fields (one field=1/60 sec in NTSC; one field= 1/50 sec in PAL).

Since the VOBU size is presented in units of sectors, as describedabove, VOBUs can be accessed using addresses in units of sectors.

On the other hand, each time entry contains address information of thecorresponding VOBU, and time difference information. This timedifference information indicates the difference between the playbacktime designated by the time entry and the VOBU playback start time.

Assuming that the time interval (time unit TMU) between two successivetime entries is 10 sec, this time entry interval corresponds to 600fields in, e.g., NTSC video.

Each VOBU entry, e.g., VOBU entry #1, includes reference picture sizeinformation 1STREF_SZ, VOBU playback time information VOBU_PB_TM, andVOBU size information VOBU_SZ.

Note that reference picture size information 1STREF_SZ represents thesize of the first reference picture (corresponding to I-picture in MPEG)of the VOBU of interest in units of sectors.

The VOBU general information included in cell VOBU table #m in FIG. 8includes I-picture end position information, as shown in FIG. 9. Thepresence of the I-picture end position information means the presence ofthe size information from the start position (address) of the VOBU ofinterest to that I-picture end position. Therefore, 1STREF_SZ(corresponding to the I-picture size of VOBU#1) in FIG. 31 correspondsto the VOBU general information included in the cell VOBU table in FIG.8.

VOBU playback time information VOBU_PB_TM in FIG. 31 represents theplayback time of the VOBU of interest in units of video fields.

The time code table included in cell time general information in FIG. 8contains information of the number of pictures and the number of sectorsin a VOBU. Since the playback time of each VOBU changes depending on thenumber of pictures and the number of sectors included there, the timecode table included in cell time general information #m in FIG. 8includes information corresponding to VOBU playback time informationVOBU_PB_TM in FIG. 31.

VOBU size information VOBU_SZ in FIG. 31 represents the size of the VOBUof interest in units of sectors. Since one ECC block corresponds to 16sectors, this VOBU size information VOBU_SZ corresponds to informationof the number of ECC blocks in a VOBU included in the time code tableshown in FIG. 8.

VOBU playback time information VOBU_PB_TM in FIG. 31 represents theplayback time of each VOBU of interest in units of video fields. Ingeneral, since one frame=one picture=two fields, information VOBU_PB_TMin FIG. 31 indicates the same information contents as the number of VOBUpictures in FIG. 8.

In summary, cell time information CTI shown in FIG. 8 (and FIG. 4)includes VOBU general information corresponding to 1STREF_SZ in the VOBUentry in FIG. 31, and cell time general information (the number of VOBUpictures and the number of ECC blocks in a VOBU) corresponding toVOBU_PB_TM and VOBU_SZ in FIG. 31.

Therefore, cell time information CTI #m shown in FIG. 8 (and FIG. 4)conceptually has contents corresponding to the VOBU entry in FIG. 31.

Cell time information CTI #1 in FIG. 31 is included in cell time controlinformation CTCI, which is included in AV data control information DA210in FIG. 4.

That is, navigation data (RTR_VMG) in FIG. 30 corresponds to controlinformation DA21 in FIG. 4 in a broad sense.

Normally, the “time interval between neighboring VOBUs” is expressed bythe number of fields in the VOBU entry. As another method, a “countvalue from a given VOBU to the next VOBU by a clock counter” may be usedto express the “time interval between neighboring VOBUs”.

For example, the “time interval between neighboring VOBUs” can beexpressed by the “difference value between the value of presentationtime stamp PTS (see FIG. 6) at the start position of one VOBU and thevalue of PTS at the start position of the immediately succeeding VOBU”.

In other words, “the time interval in a specific unit can be expressedby the difference value of the clock counter in that unit”. Such unitcan also be called a streamer object unit (SOBU).

In addition, the following remarks will be given in association with thecontents of the time code table shown in FIG. 8.

In FIG. 8, the time code table is expressed by the number of VOBUpictures, and the number of ECC blocks in a VOBU. As another embodimentof the present invention, the following method may be used. That is, thenumber of fields (one picture=two fields) included in a VOBU may be usedin place of the number of VOBU pictures. Furthermore, the number ofsectors (one ECC block=16 sectors) in an area where the VOBU of interestis recorded can be used in place of the number of ECC blocks in a VOBU.

FIG. 32 exemplifies the contents of time map general information TMAP_GIshown in FIG. 31.

This time map general information TMAP_GI includes TM_ENT_Ns indicatingthe number of time entries in that time map information, VOBU_ENT_Nsindicating the number of VOBU entries in that time map information, timeoffset TM_OSF for that time map information, and address offset ADR_OFSof that time map information.

When a value (10 seconds or equivalent) corresponding to 600 fields inNTSC video (or 500 fields in PAL video) is used as time unit TMU, timeoffset TM_OSF is used to represent the time offset within TMU.

When the VOBU size is expressed by the number of sectors, address offsetADR_OFS is used to indicate the total size of preceding VOBs (one ormore preceding VOBs) in an AV file.

FIG. 33 exemplifies the contents of time entry TM_ENT shown in FIG. 31.

This time entry TM_ENT includes VOBU_ENTN indicating the number of thecorresponding VOBU entry, TM_DIFF indicating the time difference betweenthe playback time of a VOBU designated by the time entry, and thecomputed playback time, and VOBU_ADR indicating the target VOBU address.

When time unit TMU is expressed by 600 fields in NTSC (or when time unitTMU is expressed by 500 fields in PAL), the “computed playback time”with respect to time entry #j is given by TMU×(j−1)+TM_OSF.

On the other hand, VOBU_ADR indicates the target VOBU address by thetotal size of VOBUs preceding the VOBU of interest when the VOBU size isexpressed in units of sectors.

FIG. 34 is a view for explaining the recorded contents of data area DAin FIG. 30, and a time entry point (access point) upon playing back aspecific portion (e.g., VOBU#3) of the recorded contents.

As has been described above with reference to FIG. 30, data area DArecords movie video object RTR_MOB.VOB (DA22 a-1 to DA22 a-3), stillpicture video object RTR_STO.VOB (DA23 a-1), a computer data file, andthe like.

For example, in one movie video object RTR_MOB.VOB (DA22 a-1), its dataextent/set #A stores data (video pack V_PCK, sub-picture pack SP_PCK,and the like) from logical block numbers LBN·a to LBN·a+b−1.

These logical block numbers correspond to predetermined movie addresses(M·ADR o to M·ADR b−1). A given portion of a set of these movieaddresses corresponds to VOBU#1, and the remaining portion correspondsto VOBU#2.

Likewise, a set of movie addresses corresponding to a portion of acomputer data file (extent #B) in data area DA corresponds to VOBU#3. Onthe other hand, a set of movie addresses corresponding to the remainingportion of the computer data file (extent #B) and movie addresses(M·ADRb+f) of a portion of another extent #C corresponds to VOBU#4, anda set of movie addresses of the remaining portion of extent #Ccorresponds to VOBU#5.

In the aforementioned set of VOBUs, VOBU#1 to VOBU#3 make up videoobject VOB #α, and VOBU#4 to VOBU#5 make up video object VOB#β.

In the data structure exemplified above, in order to start playback fromthe middle of, e.g., VOBU#3, that access point must be determined. Thisaccess point is assumed to be a time entry point.

In the example shown in FIG. 34, the time entry point is located at aposition separated the time difference indicated by time differenceinformation TM_DIFF in time entry TM_ENT in FIG. 33 from a positionindicated by movie address information (MADR b) of VOBU#3. This timeentry point serves as a special playback start point (or time searchpoint) indicated by time map information TMAPI.

FIG. 35 is a view for explaining an example of the directory structureof information (data files) recorded on the optical disc shown in FIG. 1in the structure shown in FIG. 30.

Even when the data structure shown in FIG. 30 is used on thedisc/apparatus side, this data structure is invisible to the user. Thedata structure that the user can actually see is a hierarchical filestructure shown in FIG. 35.

More specifically, directories such as a DVD_RTR directory, VIDEO_TSdirectory, AUDIO_TS directory, computer data file directories, and thelike are displayed on the display screen (not shown) of the rootdirectory by means of menu windows, icons, or the like in correspondencewith the types of data recorded on data area DA shown in FIG. 30.

The DVD_RTR directory shown in FIG. 35 stores file RTR.IFO of navigationdata RTR_VMG in FIG. 30, backup file RTR.BUP of RTR.IFO, fileRTR_MOV.VRO of movie video object RTR_MOV.VOB, file RTR_STO.VRO of stillpicture video object RTR_STO.VOB, file RTR_STA.VRO of additional audioobject RTR_STA.VOB for still pictures, manufacturer specification objectfile MSP.VOB, another stream object file AST.SOB, and the like.

When the DVD video recorder shown in FIG. 27 (RTR video recorder capableof real-time recording) has a directory display function shown in FIG.35, and a DVD video ROM disc is set in its disc drive 32, the VIDEO_TSdirectory in FIG. 35 is activated. In this case, when the user opens theVIDEO_TS directory, the recorded contents of the set disc are furtherdisplayed.

When the apparatus shown in FIG. 27 has a DVD audio playback function,and a DVD audio disc is set in its disc drive 32, the AUDIO_TS directoryin FIG. 35 is activated. In this case, when the user opens the AUDIO_TSdirectory, the recorded contents of the set desk are further displayed.

Likewise, when the apparatus shown in FIG. 27 has a computer dataprocessing function, and a DVD-RAM (or DVD-ROM) disc that recordedcomputer data is set in its disc drive 32, the computer data directoryin FIG. 35 is activated. In this case, when the user opens the computerdata directory, the recorded contents of the set desk are furtherdisplayed.

The user can access the recorded sources of DVD video, DVD video ROM,DVD audio, and computer data (including programs) as if he or she wereoperating a personal computer, while observing a menu screen or windowdisplay screen displayed with the directory structure shown in FIG. 35.

FIG. 36 is a schematic view for explaining a case wherein the cellplayback order of the initially recorded contents (original PGC) hasbeen changed by the user later using a user-defined PGC.

For example, video data (video object set VOBS) recorded on audio/videodata area DA2 in FIG. 5 is comprised of a set of one or more programchains PGC. Each PGC is a set of programs as sets of one or more cells,and the playback order of cells that form each program can be determinedby original PGC information (ORG_PGCI·DA210 d in FIG. 30) or auser-defined PGC information table (UD_PGCI·DA210 e in FIG. 30).

The playback time and order of cells designated by the original PGCinformation or user-defined PGC information are converted into theaddresses of VOBUs that form each of cells to be played back via a table(TMAP) in time map information TMAPI in FIG. 30.

More specifically, when playback is made based on an original PGC (thecell playback order in the initially recorded state), the VOBU addressesin the time band to be played back are obtained via time map informationtable TMAP in accordance with the contents of ORG_PGCI in FIG. 30, andplayback is made in that order.

On the other hand, when playback is made based on a PGC uniquely definedby the user (e.g., when the user has edited the playback order aftervideo recording), the VOBU addresses in the time band to be played backare obtained via time map information table TMAP in accordance with thecontents of UD_PGCI in FIG. 30, and playback is made in that order.

The cell playback order based on user-defined PGC information UD_PGCIcan be quite different from that based on original PGC informationORG_PGCI.

Note that the playback time and the addresses of VOBUs to be played backcan correspond to each other by looking up the contents of the timeentries and VOBU entries in time map information TMAPI shown in FIG. 31.

The I-picture audio position information in FIG. 9 expresses, usingsectors as a unit, the differential address value from the startposition of a VOBU of a sector that includes an audio pack of the sametime as the I-picture start time. However, the present invention is notlimited to such sector unit, and the differential address may beexpressed using the number of differential ECC blocks or the number ofVOBUs that indicates a “shift” amount, depending on differentembodiments of the present invention.

That is, the “shift” amount of a VOBU that includes an audio pack of thesame time as the I-picture start time from a VOBU that includes theI-picture of interest can be expressed using the number of VOBUs. FIG.37 shows this example.

FIG. 37 is a view for explaining problems that will occur in audio datawhen video recording is interrupted before a GOP of MPEG-encoded videodata comes to an end upon recording corresponding audio data togetherwith MPEG-encoded video data.

In a DVD video recorder that makes video recording while executing MPEGencoding, the user (or video recording timer) sometimes interrupts videorecording before a GOP (from a given I-picture to a position immediatelybefore the next I-picture) comes to an end. In such case, audio datarecorded parallel to video data is interrupted at the same time.

Upon playing back MPEG-encoded video recorded contents, since anincomplete GOP portion cannot be decoded, a process for completing thatGOP by appending correction data to the incomplete GOP is done uponencoding.

In this case, since there is no audio data for a portion (less than 0.5sec if the playback time per GOP is 0.5 sec) corresponding to theplayback time of the correction data appended to complete the GOP, soundis interrupted (abnormal sound is produced in some cases) upon videoplayback of that portion. Assume that this portion is called an audiogap.

In order to cope with sound interrupt (or abnormal sound) due to suchaudio gap upon playback, the position of this audio gap must bedetected.

The time at which the audio gap is displayed matches the time at whichthe last data of VOBU#n−1 is displayed with respect to video data.Therefore, the last display time of the audio gap period (=the time atwhich the next audio information is displayed, i.e., the time at whichsound restarts) matches the time at which the first I-picture in VOBU#nas the next VOBU is displayed. Therefore, the I-picture audio positionin FIG. 9 is information indicating the position of a VOBU whichincludes an audio pack as the audio gap end time of the same time as theI-picture start time.

More specifically, the position of specific information such as theaudio gap can be detected by exploiting the contents of the audiosynchronization information shown in FIG. 9.

That is, the start position (I-picture start time) of the “GOP completedby correction” can be specified using “I-picture audio position”information in the audio synchronization information in FIG. 9.

The presence of specific information such as the audio gap behind theI-picture in the GOP can be detected based on the most significantbit=“0” of 1-byte “I-picture audio position information”.

Also, the audio sample position that corresponds to the specificinformation like the audio gap from the I-picture start time of the GOPcan be specified by the “I-picture start audio sample number” in theaudio synchronization information in FIG. 9.

Use of the “I-picture start audio sample number” in FIG. 9 is notlimited to position detection of the audio gap, but FIG. 37 exemplifiesthat the audio synchronization information shown in FIG. 9 can beexploited in “audio gap position detection”.

According to the embodiment of the present invention, the followingeffects are obtained.

(1) When the time map information (TMAPI in FIG. 31) is available, evenwhen the user has changed the playback order using user-defined PGCinformation to be different from an original one, the VOBU from whichplayback is to start can be detected using the VOBU entries in time mapinformation TMAPI. By rewriting the user-defined PGC information withoutre-recording data while changing the initial recording order, videoplayback can be made in an arbitrary order.

(2) Since the cell configuration of a program chain to be recorded canbe corrected as needed in correspondence with the performance of a discdrive used, seamless, continuous playback or recording can beimplemented irrespective of the disc drive used.

(3) Since the audio synchronization information is provided, even whenpostrecording is done from various sound sources (digital sound sourcesgenerated at various sample rates) using dummy packs and the like (i.e.,even when the sample rate of an original sound source recorded in audiopacks is different from that of another sound source recorded in dummypacks by postrecording), synchronization (playback timing) between avideo signal recorded in video packs and the postrecorded audio signalcan be prevented from shifting.

(4) Since the audio synchronization information is provided, even whenmulti-channel recording is done using various sound sources (digitalsound sources generated at various sample rates), synchronization(playback timing) of audio signals among channels can be prevented fromshifting.

(5) Even when the contents of a specific area in video information arere-arranged on the information storage medium by, e.g., an edit process,continuous audio signal playback can be made without any sound interruptor the like.

Additional advantages and modifications will readily occur to thoseskilled in the art. Therefore, the invention in its broader aspects isnot limited to the specific details and representative embodiments shownand described herein. Accordingly, various modifications may be madewithout departing from the spirit or scope of the general inventiveconcept as defined by the appended claims and their equivalents.

1. A machine readable information storage medium for access by aninformation playback system, the information storage medium embodied asan optical disc comprising: a first area in which a video object isrecorded; and a second area in which control information is recorded,the control information including first program chain information andsecond program chain information, the first program chain informationrelating to a first program chain, the second program chain informationrelating to a second program chain, cells being specified by the controlinformation, the first program chain specifying a first playbacksequence of one part of the cells, the second program chain specifying asecond playback sequence of another part of the cells, a first cell ofthe one part of cells referring to a first region of the video object, asecond cell of the another part of cells referring to a second region ofthe video object, a part of the first region being able to overlap withthe second region to enable playback of the part of the first region,another part of the first region being able not to include the secondregion, one of the cells corresponding to a specific ID, the specific IDrelating to Main video or Sub video, and the control informationincluding I-picture end position information, wherein the controlinformation is read and provided to play back the video object by theinformation playback system, and the video object is accessed accordingto the read control information.
 2. An information playback method forinformation playback from an information storage medium embodied as anoptical disc including, a first area in which a video object isrecorded, and a second area in which control information is recorded,the control information including first program chain information andsecond program chain information, the first program chain informationrelating to a first program chain, the second program chain informationrelating to a second program chain, cells being specified by the controlinformation, the first program chain specifying a first playbacksequence of one part of the cells, the second program chain specifying asecond playback sequence of another part of the cells, a first cell ofthe one part of cells referring to a first region of the video object, asecond cell of the another part of cells referring to a second region ofthe video object, a part of the first region being able to overlap withthe second region to enable playback of the part of the first region,another part of the first region being able not to include the secondregion, one of the cells corresponding to a specific ID, the specific IDrelating to Main video or Sub video, and the control informationincluding I-picture end position information, the information playbackmethod comprising: reading the control information; and accessing andplaying back the video object based on the read control information. 3.An information recording method for recording information on aninformation storage medium embodied as an optical disc including, afirst area in which a video object is recorded, and a second area inwhich control information is recorded, the control information includingfirst program chain information and second program chain information,the first program chain information relating to a first program chain,the second program chain information relating to a second program chain,cells being specified by the control information, the first programchain specifying a first playback sequence of one part of the cells, thesecond program chain specifying a second playback sequence of anotherpart of the cells, a first cell of the one part of cells referring to afirst region of the video object, a second cell of the another part ofcells referring to a second region of the video object, a part of thefirst region being able to overlap with the second region to enableplayback of the part of the first region, another part of the firstregion being able not to include the second region, one of the cellscorresponding to a specific ID, the specific ID relating to Main videoor Sub video, and the control information including I-picture endposition information, the information recording method comprising:recording a new video object on the first area; and adding new controlinformation to the second area.
 4. An information playback system forinformation playback from an information storage medium according toclaim 1, the information playback system comprising: a reading unitconfigured to read the control information; and an accessing unitconfigured to access and to play back the video object based on the readcontrol information.